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Ginkgo Biloba

Ginkgo biloba
Evidence Level
Limited
4 Clinical Trials
6 Documented Benefits
2/5 Evidence Score

Ginkgo biloba is a popular herbal supplement derived from the leaves of the Ginkgo tree, one of the oldest living tree species. It is commonly used to support cognitive function, memory, and circulation. It is rich in flavonoids and terpene lactones that behave as antioxidants in laboratory assays, and the traditional rationale is that it improves blood flow to the brain and protects cells from oxidative damage; that rationale comes from mechanistic and animal work, not from clinical outcomes. It’s often taken for age-related cognitive decline, mental clarity, and sometimes for symptoms like tinnitus or anxiety. The large randomised trials have not been kind to those uses. Two multi-year prevention trials in nearly 6,000 older adults, one in the United States and one in France, found no reduction in dementia or Alzheimer's disease. A meta-analysis in healthy adults found effect sizes close to zero for memory, attention and executive function. Cochrane reviews of ginkgo for leg pain from poor circulation and for tinnitus were both negative. Only two narrow signals survive: short-term symptom scores in people who already carry a dementia diagnosis, which the 2026 Cochrane update rates low certainty, and a single small four week trial in generalised anxiety disorder that has never been independently replicated. Nearly all of the rigorous trials used the standardized extract EGb 761 (24% flavonol glycosides, 6% terpene lactones), so what is known applies to that extract and does not automatically transfer to non-standardized ginkgo products, which may not contain comparable levels of active compounds.

Studied Dose 120-240 mg/day standardized leaf extract, 1-2 divided doses; EGb 761 is the most studied form, though 240 mg/day is the dose used in large prevention trials that found no benefit.
Active Compound Standardized leaf extract (~24% flavonol glycosides, ~6% terpene lactones): flavonoids (quercetin, kaempferol, isorhamnetin) and terpene lactones (ginkgolides A/B/C, bilobalide). Pharmacopoeial-grade extracts also cap ginkgolic acids at under 5 parts per million, because these compounds are allergenic and cytotoxic at higher levels; cheap or non-standardized leaf products are the ones most likely to exceed that limit.

Benefits

Cognitive Function and Memory

Ginkgo biloba is heavily promoted for memory, and the trial evidence does not support that promotion. A meta-analysis of randomised trials in healthy adults pooled 1,132 participants for memory, 534 for executive function and 910 for attention and found effect sizes close to zero in all three, unrelated to age, dose or trial length. In the Ginkgo Evaluation of Memory study, 3,069 adults aged 72 to 96 took 120 mg twice daily for a median of 6.1 years and declined at the same rate as placebo in memory, attention, language, visuospatial ability and executive function, with no subgroup doing better; the same trial found no reduction in dementia or Alzheimer's disease. A separate 5 year French trial in 2,854 older adults with memory complaints, using the branded EGb 761 extract at the same dose, also found no reduction in progression to Alzheimer's disease. In mild cognitive impairment, the 2026 Cochrane update concludes ginkgo probably has little or no effect at six months. The one place a positive signal survives is people who already carry a dementia diagnosis, where that Cochrane update found small to moderate six-month improvements in global status, cognition and daily function, but rated the evidence low certainty, found extreme inconsistency between the trials, and drew it from a literature in which nearly all of the well conducted trials tested one standardized branded extract rather than generic ginkgo. The short version: ginkgo is not a memory booster for people whose memory is normal, and it is at best an uncertain option for people whose memory is not.

Supported by Trial 2, Trial 1

Circulation and Cardiovascular Health

Ginkgo may improve blood circulation by dilating blood vessels and reducing blood viscosity. That idea has been tested directly and it did not hold up. A Cochrane review of 14 randomised trials in 739 people with peripheral arterial disease pooled the 11 placebo-controlled trials, covering 477 people, and found that maximum walking distance increased by the equivalent of only about 64 metres on a flat treadmill, a difference that was not statistically significant, and the reviewers judged that publication bias had probably inflated even that. Their conclusion was that there is no evidence of clinically significant benefit for peripheral arterial disease. Cardiovascular outcomes were checked separately in the 3,069 participant Ginkgo Evaluation of Memory study, where over a median 6.1 years ginkgo produced no reduction in cardiovascular death, heart attack, angina or stroke, and the authors concluded it cannot be recommended for preventing cardiovascular disease. Ginkgo is also widely sold for cold hands and feet, and that has been tested twice in Raynaud's disease: a small 2002 trial reported fewer attacks, but a later placebo-controlled trial of the standardized EGb 761 extract in 41 patients over 10 weeks found no significant difference from placebo in the frequency, duration or severity of attacks. One genuine mechanistic finding does survive: a meta-analysis of 18 trials confirmed that ginkgo measurably lowers blood viscosity. What has never been shown is that this translates into anything a person can feel.

Supported by Trial 3

Antioxidant Properties

Ginkgo contains flavonoids and terpenoids, which act as antioxidants, neutralizing free radicals and reducing oxidative stress. That antioxidant activity is real in laboratory assays. Whether it protects anyone from aging, heart disease or neurodegenerative conditions is a separate question, and it has been tested: the multi-year randomised trials that measured dementia incidence and cardiovascular events in thousands of older adults found no reduction in either. An antioxidant effect in a test tube is a starting point for research, not a health outcome.

Supported by Trial 2, Trial 3

Anxiety and Mood

The anxiety evidence is thinner than that framing usually implies, though it is not nothing. It rests largely on a single 4 week randomised trial in 107 patients with generalised anxiety disorder or adjustment disorder with anxious mood, in which 480 mg and 240 mg per day of the branded EGb 761 extract lowered Hamilton anxiety scores by 14.3 and 12.1 points against 7.8 on placebo, with a dose-response trend. That is a real positive result. It is also one small short trial, designed and analysed by authors connected to the extract manufacturer, testing a specific branded extract rather than generic ginkgo, and never independently replicated at comparable scale. The Cochrane review of ginkgo in dementia separately reported that results for mood and depression were inconsistent. The explanation offered for how ginkgo would reduce anxiety, better cerebral blood flow and antioxidant activity, is speculation rather than anything that was measured in that trial.

Supported by Trial 1, Trial 3

Tinnitus and Hearing

Ginkgo is widely sold for tinnitus, and two Cochrane reviews have examined it. The 2013 review of four trials in 1,543 participants, all at low risk of bias, found no evidence of effectiveness when tinnitus was the primary complaint. The 2022 update, covering 12 trials and 1,915 participants, concluded ginkgo may make little or no difference to tinnitus severity, loudness or quality of life, and rated that evidence low to very low certainty, since most of those trials were poorly blinded or poorly reported and tinnitus responds unusually strongly to placebo. Neither review tested the common claim that ginkgo works better when tinnitus is linked to poor blood flow. The only positive observation in either review came from a trial of people with mild to moderate dementia who happened to have low-level tinnitus to begin with, where reductions of 1.5 and 0.7 points on a 10 point scale were seen and the reviewers described the practical significance as unclear.

Supported by Trial 4, Trial 1

Eye Health

The eye evidence is very small, and where it has been retested it has not held up. A Cochrane review of ginkgo for age-related macular degeneration found only two randomised trials with 119 people between them, both lasting six months, and one of them without a placebo arm. Both reported some positive effect on vision, but the results could not be pooled and neither reported adverse effects or quality of life. The reviewer's conclusion was that whether people with macular degeneration should take ginkgo has not been answered by research to date. For glaucoma, a 27 patient crossover trial in 2003 reported that four weeks of 120 mg per day improved visual field indices in normal tension glaucoma. A later randomised crossover trial used the same dose, the same 4 week phases and the same washout in 35 patients, was powered to detect an effect as large as the one first reported, and found no effect on visual field or contrast sensitivity. A 2025 systematic review pooling 8 studies and 428 patients found no effect on intraocular pressure or on either visual field measure. This is an open research question at best, not a reason to take ginkgo for your eyes.

Supported by Trial 4, Trial 1

Mechanism of action

1

Antioxidant Activity

Mechanism: Flavonoids in ginkgo act as free radical scavengers, neutralizing reactive oxygen species (ROS) and reducing oxidative stress. This protects cells, particularly neurons and vascular tissues, from damage linked to aging, neurodegenerative diseases, and cardiovascular issues. Whether this mitigates cellular damage in dementia, heart disease or retinal degeneration is a hypothesis rather than a finding. The large randomised trials that measured dementia incidence and cardiovascular events directly, over five to six years in thousands of older adults, found no reduction in either.

2

Improved Blood Flow and Vasodilation

Mechanism: Ginkgo enhances microcirculation by promoting vasodilation (via nitric oxide pathways) and reducing blood viscosity. Ginkgolides inhibit platelet-activating factor (PAF), which reduces platelet aggregation and prevents excessive blood clotting. The blood-flow mechanism itself is not imaginary: a meta-analysis of 18 randomised trials confirmed a real reduction in blood viscosity. What has not been shown is the clinical step usually attached to it. The Cochrane review of intermittent claudication found no clinically significant benefit for peripheral arterial disease, the large cognition trials were null, and in glaucoma the one early positive trial was not reproduced when a later randomised trial retested it at the same dose. A measurable change in a blood parameter is not the same thing as a benefit a person experiences.

3

Neuroprotection

Mechanism: Ginkgo protects neurons by reducing oxidative damage, stabilizing mitochondrial function, and modulating neurotransmitter activity (e.g., enhancing cholinergic signaling). Bilobalide may inhibit excitotoxicity by regulating glutamate release. This neuroprotection account comes from cell and animal work. In humans it did not slow cognitive decline: across a median 6.1 years, 3,069 older adults taking 240 mg per day declined at the same rate as placebo in memory, attention, language, visuospatial ability and executive function, and the 2026 Cochrane update concludes ginkgo probably has little or no effect in mild cognitive impairment. Preclinical neuroprotection has repeatedly failed to translate for many compounds, and ginkgo is one of the better documented examples.

4

Anti-Inflammatory Effects

Mechanism: Ginkgolides, particularly ginkgolide B, inhibit PAF, a mediator of inflammation, reducing inflammatory responses in tissues. Flavonoids also suppress pro-inflammatory cytokines. The suggestion that this relieves tinnitus or cardiovascular disease has been tested at the clinical level rather than left hypothetical, and it was not supported. Cochrane reviews of ginkgo for tinnitus in 2013 and again in 2022 found no benefit, the second at low to very low certainty, and the Cochrane review of ginkgo for peripheral arterial disease found no clinically significant benefit.

5

Modulation of Neurotransmitters

Mechanism: Ginkgo may influence serotonin, dopamine, and acetylcholine systems, potentially enhancing mood and cognitive processing. It may also inhibit monoamine oxidase (MAO), increasing neurotransmitter availability. Could contribute to reduced anxiety, though the evidence there is a single small short trial of a branded extract. Two further cautions belong here. Monoamine oxidase inhibition by ginkgo was demonstrated in rat brain tissue, but when it was looked for directly in living human brains by PET imaging, in people who had taken 120 mg per day for a month, neither enzyme was inhibited, so this part of the mechanism should not be assumed to operate in people at supplement doses. And the cognitive half of this proposition has now been tested directly in randomised trials with many thousands of participants and was not confirmed.

6

Mitochondrial and Cellular Protection

Mechanism: Ginkgo stabilizes mitochondrial membranes and enhances energy production, protecting cells from apoptosis (programmed cell death) under stress. This work is in cells and animal models. When the corresponding human outcomes were measured directly, ginkgo did not reduce dementia, stroke, heart attack or cardiovascular death across multi-year randomised trials in thousands of older adults.

Clinical trials

1
Cochrane Review: Ginkgo for Cognitive Impairment & Dementia

Cochrane systematic review pooling 36 randomized, placebo-controlled trials of Ginkgo biloba extract (most using the standardized EGb 761® form) across cognitive impairment and dementia of varying severity.

36 trials; thousands of participants with cognitive impairment or dementia.

Concluded that the evidence Ginkgo biloba produces any predictable, clinically significant benefit for cognitive impairment or dementia is inconsistent and unreliable, with the more recent, larger and better designed trials largely negative. Of the four most recent trials to report, three found no difference from placebo. A subgroup analysis restricted to 925 people with Alzheimer's disease showed no consistent benefit either. Ginkgo was as safe as placebo. This review has since been replaced by a 2026 Cochrane update covering 82 studies and 10,613 participants, which reaches a more differentiated conclusion: probably little or no effect in mild cognitive impairment, uncertain effect in people with subjective memory complaints, and possible small to moderate six-month benefits in people who already have dementia, rated low certainty.

2
Meta-Analysis: Ginkgo in Healthy Adults

Meta-analysis of placebo-controlled trials testing whether Ginkgo biloba enhances cognition in healthy people, pooling memory, executive function, and attention outcomes.

Healthy adults (1,132 / 534 / 910 participants across the three cognitive domains).

Effect sizes were essentially zero and non-significant across memory (d = -0.04), executive function (d = -0.05) and attention (d = -0.08), and meta-regression showed they were unrelated to participant age, trial duration, daily dose, total dose or sample size. The authors concluded ginkgo has no ascertainable cognitive-enhancing effect in healthy individuals, which does not support memory booster marketing for people without cognitive impairment. The same conclusion emerged from the largest trial ever run on ginkgo: in the Ginkgo Evaluation of Memory study, 3,069 US adults aged 72 to 96 took 120 mg twice daily for a median of 6.1 years and showed no slower decline than placebo in any cognitive domain, with no reduction in dementia or Alzheimer's disease. A separate 5 year French trial in 2,854 older adults with memory complaints, using the branded EGb 761 extract, likewise found no reduction in progression to Alzheimer's disease.

3
Cochrane Review: Ginkgo for Intermittent Claudication

Cochrane systematic review of 14 randomized placebo-controlled trials of Ginkgo biloba for intermittent claudication (leg pain from peripheral arterial disease), assessing pain-free walking distance.

14 trials, 739 participants with peripheral arterial disease.

Ginkgo produced only a small, statistically non-significant increase in pain-free walking distance versus placebo, with no clinically meaningful benefit for intermittent claudication. Effectively a no-benefit conclusion for circulation symptoms at studied doses. The reviewers also judged that publication bias had probably inflated even the small effect they measured. Cardiovascular outcomes were checked separately in the Ginkgo Evaluation of Memory study, where over a median 6.1 years ginkgo produced no reduction in cardiovascular death, heart attack, angina or stroke, and the authors concluded it cannot be recommended for preventing cardiovascular disease. Two secondary findings from that trial cut in opposite directions and neither is established: there were numerically more haemorrhagic strokes on ginkgo (16 versus 8, not statistically significant) and fewer peripheral vascular disease events on ginkgo (12 versus 23, nominally significant).

4
Cochrane Review: Ginkgo for Tinnitus

Cochrane systematic review evaluating Ginkgo biloba in adults whose primary complaint was tinnitus (ringing in the ears).

Adults with primary tinnitus across the included trials.

Found no evidence that Ginkgo biloba is effective when tinnitus is the primary complaint. A clearly negative review for the common idea of ginkgo for ringing ears, though the picture may differ where tinnitus accompanies dementia. A 2022 Cochrane update reached the same place from a wider search covering 12 trials and 1,915 participants, although only two of those trials, with 85 participants between them, could be pooled for the main severity outcome: ginkgo may make little or no difference to tinnitus severity, loudness or health-related quality of life, with the certainty of that evidence rated low to very low because of poor blinding and the strong placebo response typical of tinnitus trials.

Side effects and drug interactions

Common Potential side effects

Gastrointestinal: Nausea, upset stomach, diarrhea, or constipation.
Neurological: Headaches, dizziness, or vertigo, particularly at higher doses.
Allergic Reactions: Skin rash or itching in sensitive individuals.
Bleeding risk: the evidence points two ways and both halves matter. A systematic review of published case reports found 15 bleeding events temporally linked to ginkgo, 8 of them intracranial, with elevated bleeding times where measured; however 13 of those 15 patients had other bleeding risk factors and only 6 reports confirmed that bleeding stopped and did not recur after ginkgo was withdrawn. Against that, a meta-analysis of 18 randomised trials in 1,985 adults found no effect of standardized ginkgo extract on ADP-induced platelet aggregation, fibrinogen, prothrombin time or activated partial thromboplastin time, and the large multi-year trials reported adverse event rates no different from placebo. One detail in the largest of those trials runs the other way and is worth knowing: there were 16 haemorrhagic strokes on ginkgo versus 8 on placebo, a difference that was not statistically significant but that points in the same direction as the case reports. The practical reading is that ginkgo is unlikely to cause bleeding in an otherwise healthy person, but the reported cases are serious enough that anyone taking anticoagulants or antiplatelet drugs, anyone with a bleeding disorder, and anyone facing surgery should treat the risk as real and speak to a clinician first.
Seizures: this concern is more specific than it sounds. Ginkgo seeds contain ginkgotoxin, a compound that interferes with vitamin B6 dependent GABA synthesis and can provoke seizures; leaf extracts contain far less of it, but the concern has not been fully retired. Separately, there is a reported death from a breakthrough seizure in a man taking phenytoin and valproate whose blood levels of both drugs were subtherapeutic at autopsy, with induction of the CYP2C19 enzyme by ginkgo proposed as the explanation for why his medication stopped working; the authors of that report note one further published instance of ginkgo apparently provoking seizure activity in someone on anticonvulsant therapy. These are individual cases, causation was not proven, and several supplements were involved at once in the fatal one, but the mechanism is plausible and the outcome was fatal. Anyone with epilepsy, or taking an anticonvulsant for any reason, should not take ginkgo without their neurologist's agreement.
Allergic Reactions: Severe allergic reactions (e.g., anaphylaxis) are rare but possible.
Cardiovascular: Palpitations or increased heart rate in some users.
Psychiatric: Anxiety or restlessness, though uncommon, may occur, especially at high doses.

Important Drug interactions

Anticoagulants (warfarin, apixaban, rivaroxaban) and antiplatelet drugs (aspirin, clopidogrel): the controlled data are more reassuring than ginkgo's reputation. A randomised crossover study in healthy volunteers found that ginkgo at recommended doses did not change INR, platelet aggregation, warfarin clearance or CYP2C9 activity, and a meta-analysis of 18 randomised trials found no effect on standard clotting parameters. But published case reports do describe serious bleeds, including intracranial bleeds, in ginkgo users. Do not start ginkgo on your own while taking these drugs, and tell your prescriber if you already are. Before surgery: the usual pre-operative advice is to stop herbal supplements including ginkgo one to two weeks before a planned procedure, and that remains the sensible default even though the controlled clotting data are equivocal, because the downside of stopping is nothing and the downside of a surgical bleed is not. Anticonvulsants (phenytoin, valproate): this is the interaction that deserves the most respect. Ginkgo can induce CYP2C19, which helps clear both drugs, and a fatal breakthrough seizure has been reported in a patient on both whose blood levels were subtherapeutic while he was taking ginkgo among other supplements. People with epilepsy should avoid ginkgo unless their neurologist agrees. SSRIs and other serotonergic medicines: this warning is usually justified by the idea that ginkgo inhibits monoamine oxidase, which was shown in rat brain tissue but was not found when researchers imaged the brains of people taking 120 mg per day for a month, so the practical risk appears low; mention it to your prescriber rather than worry about it. Other prescription medicines: because ginkgo can induce CYP2C19, it may lower blood levels of drugs cleared by that pathway, so check with a pharmacist if you take anything with a narrow safety margin.

Standardized & branded forms of Ginkgo Biloba

Trademarked Ginkgo Biloba extracts with their own clinical trials and dedicated profiles. Most Ginkgo Biloba research is run on one of these standardized forms:

Cognitive
EGb 761® (Standardized Ginkgo biloba Extract)
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Frequently asked questions about Ginkgo Biloba

How much ginkgo biloba should I take?

Studies typically use 120 to 240 mg per day of a standardized leaf extract such as EGb 761, split into two or three doses. The extract is standardized to about 24% flavone glycosides and 6% terpene lactones, so look for those figures on the label.

How long does ginkgo take to work?

Trials of ginkgo usually run at least 8 to 12 weeks, and the two large prevention trials ran for 5 and 6 years, so nothing about it is fast. It is worth saying plainly that more time did not rescue the results: in the trials that ran for years, the ginkgo groups did no better than placebo on memory or on dementia risk. If you do try it, judge it over a couple of months rather than a couple of days, and be prepared for the honest possibility that there is nothing to notice.

Does ginkgo thin the blood?

Ginkgo can have a mild blood-thinning effect. If you take anticoagulants or antiplatelet drugs such as warfarin or aspirin, have a bleeding disorder, or are scheduled for surgery, talk to your doctor first and generally stop it about two weeks before any procedure.

What is ginkgo biloba good for?

Ginkgo is most popular for memory, cognitive support and circulation, and has also been studied for age-related eye and ear concerns. The honest answer is that the research on those popular uses is mostly negative rather than mixed. Two multi-year randomised trials in nearly 6,000 older adults found no reduction in dementia or Alzheimer's disease, a meta-analysis in healthy adults found no memory benefit at any dose or duration, and Cochrane reviews of leg pain from poor circulation and of tinnitus were both negative. The one area where a weak signal survives is short-term symptom scores in people who already have a dementia diagnosis, and the current Cochrane review rates even that low certainty. Treat ginkgo as an unproven option rather than a memory booster.

What is Ginkgo Biloba?

Ginkgo biloba is a popular herbal supplement derived from the leaves of the Ginkgo tree, one of the oldest living tree species. It is commonly used to support cognitive function, memory, and circulation.

What is Ginkgo Biloba used for?

Ginkgo Biloba is researched primarily for Cognitive and Mood & Mental Health. Ginkgo biloba is heavily promoted for memory, and the trial evidence does not support that promotion. A meta-analysis of randomised trials in healthy adults pooled 1,132 participants for memory, 534 for executive function and 910 for attent…

What is the recommended dosage of Ginkgo Biloba?

The clinically studied dose is 120-240 mg/day standardized leaf extract, 1-2 divided doses; EGb 761 is the most studied form, though 240 mg/day is the dose used in large prevention trials that found no benefit. Always follow the product label and check with a healthcare provider for personal advice.

Is Ginkgo Biloba safe, and does it have side effects?

For most healthy adults, Ginkgo Biloba is well tolerated at studied doses. Reported effects can include: Gastrointestinal: Nausea, upset stomach, diarrhea, or constipation. Neurological: Headaches, dizziness, or vertigo, particularly at higher doses. It may also interact with some medications. Ginkgo Biloba is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Ginkgo Biloba interact with any medications?

Possible interactions include: Anticoagulants (warfarin, apixaban, rivaroxaban) and antiplatelet drugs (aspirin, clopidogrel): the controlled data are more reassuring than ginkgo's reputation. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Ginkgo Biloba?

NutraSmarts rates the evidence for Ginkgo Biloba as Limited (2 out of 5). It is backed by 4 clinical trials and 21 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(21 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Birks J, Grimley Evans J. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database Syst Rev. 2009;2009(1):CD003120. doi: 10.1002/14651858.CD003120.pub3.PubMedUsed to support: Systematic review pooling 36 randomised, double-blind, placebo-controlled trials in people with acquired cognitive impairment or dementia of any severity, most of them testing the standardized EGb 761 extract at high or low dose. Most trials were small and ran under three months; the nine six-month trials were the more recent and better conducted ones. Among the four most recent trials to report, three found no difference from placebo and one found very large effects. A subgroup analysis restricted to 925 people with Alzheimer's disease showed no consistent pattern of benefit. The reviewers concluded that the evidence of predictable, clinically significant benefit is inconsistent and unreliable, that many early trials used unsatisfactory methods, and that publication bias could not be excluded. Adverse events did not differ from placebo. The main limitation for a reader today is age: this 2009 review has been superseded by a 2026 Cochrane update covering more than twice as many studies.
  2. Laws KR, Sweetnam H, Kondel TK. Is Ginkgo biloba a cognitive enhancer in healthy individuals? A meta-analysis. Hum Psychopharmacol. 2012;27(6):527-33. doi: 10.1002/hup.2259.PubMedUsed to support: Meta-analysis of randomised placebo-controlled trials of ginkgo in healthy adults with no cognitive impairment, pooling 1,132 participants for memory, 534 for executive function and 910 for attention. Effect sizes were close to zero and non-significant in all three domains, and meta-regression showed they were unrelated to participant age, trial duration, daily dose, total dose or sample size, so the null result cannot be dismissed as underdosing or trials that were too short. The authors concluded ginkgo has no ascertainable positive effect on cognition in healthy people. The limitation is scope: this says nothing about people who already have dementia, which is a separate question with separate and much weaker evidence.
  3. Nicolaï SP, Kruidenier LM, Bendermacher BL, Prins MH, Stokmans RA, Broos PP, Teijink JA. Ginkgo biloba for intermittent claudication. Cochrane Database Syst Rev. 2013;2013(6):CD006888. doi: 10.1002/14651858.CD006888.pub3.PubMedUsed to support: Systematic review of 14 randomised trials in 739 people with intermittent claudication caused by peripheral arterial disease. Pooling the 11 placebo-controlled trials with 477 participants, absolute claudication distance increased by the equivalent of roughly 64 metres on a flat treadmill, a difference that was not statistically significant, and the reviewers judged that publication bias had probably inflated even that figure. Their conclusion was that there is no evidence of clinically significant benefit for patients with peripheral arterial disease. One limitation worth naming: this is a diagnosed disease population, so it does not directly test the vaguer marketing claim about improving circulation in generally healthy people, which is a different and far less studied question.
  4. Hilton MP, Zimmermann EF, Hunt WT. Ginkgo biloba for tinnitus. Cochrane Database Syst Rev. 2013;2013(3):CD003852. doi: 10.1002/14651858.CD003852.pub3.PubMedUsed to support: Systematic review of four randomised trials with 1,543 participants, all assessed as being at low risk of bias, which is unusually strong for this literature. In the three trials totalling 1,143 people whose primary complaint was tinnitus, there was no evidence that ginkgo was effective. The single trial in 400 people with mild to moderate dementia who happened to have low-level tinnitus showed small reductions of 1.5 and 0.7 points on a 10 point scale in vascular dementia and Alzheimer's disease respectively, and the reviewers described the practical clinical significance of that as unclear. Side effect rates were low. The limitation is that this 2013 review has been superseded by a 2022 Cochrane update, which searched more widely and included 12 trials with 1,915 participants but could pool only 85 participants for its main severity outcome, and which reached the same conclusion at low to very low certainty.
  5. DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA. 2008;300(19):2253-62..PubMedUsed to support: Randomised, double-blind, placebo-controlled trial in 3,069 US community volunteers aged 75 and over, with either normal cognition or mild cognitive impairment, given 120 mg of ginkgo extract twice daily or placebo and followed for a median of 6.1 years, with dementia diagnosed by an expert consensus panel. Ginkgo did not reduce all-cause dementia (hazard ratio 1.12) or Alzheimer's disease (1.16), and did not slow progression to dementia among those who started with mild cognitive impairment. Dropout was low at 6.3 percent and adverse event profiles matched placebo. This is the largest and most rigorous test ever run of the claim that ginkgo protects the aging brain, and the result is negative. The extract was supplied by its manufacturer, but the trial was independently conducted and publicly funded, which makes the null result difficult to attribute to bias.
  6. Snitz BE, O'Meara ES, Carlson MC, et al. Ginkgo biloba for preventing cognitive decline in older adults: a randomized trial. JAMA. 2009;302(24):2663-70..PubMedUsed to support: Prespecified cognitive analysis of the same 3,069 participant trial, tracking rate of change over a median 6.1 years on the Modified Mini-Mental State Examination, the ADAS-Cog, and neuropsychological domains of memory, attention, visuospatial ability, language and executive function. Annual decline was effectively identical between 240 mg per day of ginkgo and placebo in every single domain, and no subgroup did better, with no modification of effect by age, sex, race, education, APOE e4 status or baseline mild cognitive impairment. This is the direct test of the everyday claim that ginkgo keeps memory sharp with age, and it found nothing. Participants were 72 to 96 years old, so it does not speak to younger users, though the meta-analysis in healthy adults covers that gap and is also null.
  7. Vellas B, Coley N, Ousset PJ, et al. Long-term use of standardised Ginkgo biloba extract for the prevention of Alzheimer's disease (GuidAge): a randomised placebo-controlled trial. Lancet Neurol. 2012;11(10):851-9..PubMedUsed to support: Randomised, double-blind, placebo-controlled trial in France enrolling 2,854 adults aged 70 and over who had spontaneously reported memory complaints to their primary care doctor, given 120 mg of the standardized EGb 761 extract twice daily or matched placebo and followed for 5 years. Conversion to probable Alzheimer's disease occurred in 61 ginkgo participants versus 73 on placebo, a difference that was not statistically significant (hazard ratio 0.84, 95 percent confidence interval 0.60 to 1.18), and there were no differences in death, stroke or haemorrhagic events. The trial was funded by the manufacturer of the extract, which matters in the opposite of the usual direction: a sponsor-funded trial of the sponsor's own branded extract, at the exact dose that ginkgo marketing points to, still could not show a benefit.
  8. Wieland LS, Ludeman E, Chi Y, et al. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database Syst Rev. 2026;2(2):CD013661..PubMedUsed to support: The current Cochrane systematic review of ginkgo for cognitive impairment and dementia, covering 82 studies and 10,613 participants, which replaces the 2009 review that this page previously relied on. It separates questions the older review lumped together. In people with mild cognitive impairment (12 studies, 1,913 participants) ginkgo probably has little or no effect at six months on global clinical status, cognition or daily activities. In people with subjective memory complaints the effect on global status is uncertain and adverse events may be more common at three months. In people with multiple sclerosis and cognitive problems there is probably no benefit. In people who already have a dementia diagnosis (13 studies, 3,288 participants) there may be small to moderate six-month benefits for global status, cognition and daily function. That last finding is the only positive result in the review, and its limitations are severe: the reviewers rate it low certainty, statistical inconsistency between trials was extremely high, and only four of the 82 studies were at low risk of bias in all domains. Nearly all of the well conducted trials in this literature have also tested one standardized branded extract rather than the generic ginkgo products most people buy.
  9. Kuller LH, Ives DG, Fitzpatrick AL, et al. Does Ginkgo biloba reduce the risk of cardiovascular events?. Circ Cardiovasc Qual Outcomes. 2010;3(1):41-7..PubMedUsed to support: Preplanned secondary cardiovascular analysis of the 3,069 participant Ginkgo Evaluation of Memory study, with events classified using Cardiovascular Health Study methods over a mean 6.1 years of 240 mg per day of the EGb 761 extract. There was no difference from placebo in coronary heart disease death, myocardial infarction, angina or stroke, and the authors concluded ginkgo cannot be recommended for preventing cardiovascular disease. Two secondary details cut in opposite directions and neither should be leaned on: there were numerically more haemorrhagic strokes on ginkgo (16 versus 8, not statistically significant), and fewer peripheral vascular disease events on ginkgo (12 versus 23, nominally significant at p = 0.04). Both come from many comparisons in one elderly population and are hypothesis-generating at best.
  10. Kellermann AJ, Kloft C Is there a risk of bleeding associated with standardized Ginkgo biloba extract therapy? A systematic review and meta-analysis. Pharmacotherapy. 2011;31(5):490-502..PubMedUsed to support: Meta-analysis of 18 randomised controlled trials in 1,985 adults, 87 percent of whom were patients with dementia, peripheral artery disease or diabetes rather than healthy volunteers, examining whether standardized ginkgo extract changes the blood measurements that predict bleeding. Ginkgo significantly reduced blood viscosity but had no significant effect on ADP-induced platelet aggregation, fibrinogen concentration, activated partial thromboplastin time or prothrombin time. Small shortenings of clotting time in the subgroups taking 240 mg per day or more were judged not clinically relevant. This is the strongest evidence that routine ginkgo does not meaningfully thin the blood, but it measures laboratory parameters rather than counting actual bleeding events, so it reduces rather than eliminates the concern raised by published case reports.
  11. Bent S, Goldberg H, Padula A, et al. Spontaneous bleeding associated with ginkgo biloba: a case report and systematic review of the literature: a case report and systematic review of the literature. J Gen Intern Med. 2005;20(7):657-61..PubMedUsed to support: Systematic review of published case reports of bleeding in people taking ginkgo, identifying 15 reports with a temporal association, including 8 episodes of intracranial bleeding, and elevated bleeding times in the three cases where this was measured. The reviewers judged a possible causal association. The limitations are the reason this cannot settle the question on its own: 13 of the 15 patients had other identifiable bleeding risk factors, and only 6 reports documented both that ginkgo was stopped and that bleeding did not recur. Case reports cannot establish causation or estimate how often this happens, which is why this evidence sits alongside, rather than above, the randomised trial data on clotting parameters.
  12. Jiang X, Williams KM, Liauw WS, et al. Effect of ginkgo and ginger on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects. Br J Clin Pharmacol. 2005;59(4):425-32..PubMedUsed to support: Open-label, three-way crossover study in 12 healthy men given a single 25 mg dose of warfarin alone, or after 7 days of pretreatment with a recommended dose of a quality-controlled ginkgo product, with dosing continued for 7 days afterwards. Ginkgo did not change the international normalised ratio, platelet aggregation, warfarin enantiomer clearance, protein binding or CYP2C9 activity. The limitations are that these were 12 healthy young men receiving a single warfarin dose over a short period, not patients on stable long-term anticoagulation with other illnesses, so this argues against a large pharmacokinetic interaction without ruling out problems in real anticoagulated patients.
  13. Kupiec T, Raj V Fatal seizures due to potential herb-drug interactions with Ginkgo biloba. J Anal Toxicol. 2005;29(7):755-8..PubMedUsed to support: Case report of a 55-year-old man who died of a breakthrough seizure while taking the anticonvulsants phenytoin and valproate, with autopsy showing subtherapeutic blood levels of both drugs despite no evidence he had stopped taking them. He was self-medicating with numerous herbal supplements, prominently ginkgo, and the authors propose ginkgo induction of the CYP2C19 enzyme as the mechanism that lowered his anticonvulsant levels; ginkgo seeds also contain a neurotoxin known to provoke seizures. This is a single case involving several supplements at once, with no rechallenge and no proof of causation, and the authors could identify only one other published instance of ginkgo apparently provoking seizure activity during anticonvulsant therapy. It is nonetheless the specific reason the safety information on this page singles out anticonvulsants instead of lumping them together with other interactions.
  14. Sereda M, Xia J, Scutt P, et al. Ginkgo biloba for tinnitus. Cochrane Database Syst Rev. 2022;11(11):CD013514..PubMedUsed to support: The current Cochrane systematic review of ginkgo for tinnitus, covering 12 randomised trials with 1,915 participants, which updates the 2013 review. On the primary outcome of tinnitus severity, only two trials with 85 participants between them could be pooled, and they differed from placebo by 1.35 points on a 100-point Tinnitus Handicap Inventory, which is neither statistically nor clinically meaningful. Single trials found little to no difference in tinnitus loudness or in health-related quality of life. Risk of bias was high or unclear in most of the trials because of poor reporting of allocation concealment and blinding, and the reviewers rated the certainty of the evidence low to very low, noting that tinnitus produces a particularly strong placebo response. On the safety side, no serious adverse effects including bleeding or seizures occurred in either group across four trials with 1,154 participants.
  15. Evans JR Ginkgo biloba extract for age-related macular degeneration. Cochrane Database Syst Rev. 2013;2013(1):CD001775..PubMedUsed to support: Systematic review of randomised trials of ginkgo extract for age-related macular degeneration, which located only two trials randomising 119 people in total, both lasting six months: a French study of 20 people given EGb 761 at 160 mg per day versus placebo, and a German study of 99 people comparing two doses of EGb 761 with no placebo arm. Both reported some positive effect on vision, but the results could not be pooled and neither reported adverse effects or quality of life. The reviewer's conclusion was that whether people with macular degeneration should take ginkgo has not been answered by research to date. That is an absence of evidence rather than evidence of benefit, which is why macular degeneration is not an established use for ginkgo.
  16. Quaranta L, Bettelli S, Uva MG, et al. Effect of Ginkgo biloba extract on preexisting visual field damage in normal tension glaucoma. Ophthalmology. 2003;110(2):359-62; discussion 362-4..PubMedUsed to support: Randomised, placebo-controlled, double-masked crossover study in 27 patients with bilateral visual field damage from normal tension glaucoma, given 40 mg of ginkgo extract three times daily for 4 weeks, then an 8-week washout, then 4 weeks of placebo, with the order reversed in half the patients. Visual field mean deviation and corrected pattern standard deviation both improved significantly over the ginkgo phase, with no change in intraocular pressure, blood pressure or heart rate, and the authors concluded that ginkgo appeared to improve preexisting visual field damage in some patients. The decisive limitation is what happened afterwards: a later randomised crossover trial in 35 patients used the same dose and the same schedule, was powered to detect an effect this large, and found none. Visual field indices are also noisy and subject to learning effects across repeated testing. Read this as an early observation that did not replicate rather than as grounds for using ginkgo to treat glaucoma.
  17. Guo X, Kong X, Huang R, et al. Effect of Ginkgo biloba on visual field and contrast sensitivity in Chinese patients with normal tension glaucoma: a randomized, crossover clinical trial. Invest Ophthalmol Vis Sci. 2014;55(1):110-6..PubMedUsed to support: Randomised, placebo-controlled, crossover trial in 35 Chinese patients newly diagnosed with normal tension glaucoma, deliberately repeating the regimen of the earlier positive study: 40 mg of ginkgo extract three times daily for 4 weeks, an 8 week washout, then 4 weeks of the other treatment, with the order randomised. Changes in visual field mean deviation and in contrast sensitivity did not differ by treatment received or by sequence, and the trial had 80 percent power to detect a difference as large as the one previously reported. This is the attempted replication of the 2003 glaucoma result, and it failed. Its limitations are that 35 patients is still a small trial and each phase lasted only 4 weeks, so it does not exclude a benefit that takes longer than a month to appear.
  18. Prinz J, Prokosch V, Wang X, et al. Efficacy of Ginkgo biloba on parameters in glaucoma: A systematic review. PLoS One. 2025;20(2):e0314644..PubMedUsed to support: Systematic review pooling 8 studies with 428 patients of average age 51 and a median follow-up under 4 months, covering ginkgo extract given both to people with glaucoma and to healthy volunteers. Ginkgo was not associated with any change in intraocular pressure, visual field mean deviation, corrected pattern standard deviation or heart rate, either from baseline or in comparison with control groups. The reviewers concluded that the evidence is not sufficient to conclude that ginkgo affects any of these measures. Their own stated limitation is the short follow-up of the included studies, which matters because glaucoma progresses over years, so this cannot rule out a slow effect; what it does show is that the early positive visual field finding has not been borne out.
  19. Bredie SJ, Jong MC No significant effect of ginkgo biloba special extract EGb 761 in the treatment of primary Raynaud phenomenon: a randomized controlled trial. J Cardiovasc Pharmacol. 2012;59(3):215-21..PubMedUsed to support: Randomised, double-blind, placebo-controlled trial in 41 people with primary Raynaud's disease, given 120 mg of the standardized EGb 761 extract twice daily or placebo for 10 weeks after a 2 week run-in period. Daily attack frequency fell by 33 percent on ginkgo and 31 percent on placebo, a difference that was not significant, and there was no difference in the duration or severity of attacks either. Tolerability was good, with fewer adverse events reported on ginkgo than on placebo. This is the closest thing to a direct test of the popular idea that ginkgo helps cold hands and feet, and it is negative. Its limitation is size: 41 patients is a pilot, so it argues against a large benefit rather than a small one, and it studied diagnosed Raynaud's disease rather than ordinary cold extremities.
  20. Fowler JS, Wang GJ, Volkow ND, et al. Evidence that gingko biloba extract does not inhibit MAO A and B in living human brain. Life Sci. 2000;66(9):PL141-6..PubMedUsed to support: Brain imaging study in 10 people who took 120 mg per day of the EGb 761 extract for one month, using PET scanning with two radiotracers to measure the activity of monoamine oxidase A and monoamine oxidase B directly in the living human brain. Neither enzyme was inhibited. This matters because inhibition of monoamine oxidase, which had been demonstrated in rat brain tissue, is the usual explanation offered both for ginkgo's supposed effects on mood and for warnings about combining it with antidepressants. The limitations are that this was 10 people at one dose for one month, so it cannot exclude effects at higher doses or on other neurotransmitter systems, but it is direct human evidence against that specific mechanism.
  21. Woelk H, Arnoldt KH, Kieser M, et al. Ginkgo biloba special extract EGb 761 in generalized anxiety disorder and adjustment disorder with anxious mood: a randomized, double-blind, placebo-controlled trial. J Psychiatr Res. 2007;41(6):472-80..PubMedUsed to support: Randomised, double-blind, placebo-controlled trial in 107 patients with generalised anxiety disorder or adjustment disorder with anxious mood, randomised to 480 mg per day of the branded EGb 761 extract, 240 mg per day, or placebo for 4 weeks. Hamilton anxiety scale scores fell by 14.3 and 12.1 points on the high and low ginkgo doses versus 7.8 on placebo, both significantly better than placebo, with a dose-response trend, and every secondary outcome favoured ginkgo. This is a real positive result and the strongest single piece of evidence for any mood-related use of ginkgo. Its limitations are why it is not treated as established: one small trial, only 4 weeks long, conducted and analysed by authors connected to the extract manufacturer, testing one specific branded extract rather than generic ginkgo, and never independently replicated at a comparable scale.