Benefits
Fasting blood sugar and HbA1c alongside glucose-lowering medicines
In a 3-month double-blind trial in 92 adults with advanced type 2 diabetes who needed insulin, 500 mg of nettle leaf extract every 8 hours, added to their usual oral medicines, lowered fasting glucose, 2-hour post-meal glucose and HbA1c more than placebo, with no change in kidney or liver markers. EU reviewers noted the extract differs from standard nettle leaf preparations.
Fasting glucose across pooled trials
A meta-analysis of 8 randomized trials (401 adults with type 2 diabetes) found fasting blood sugar about 18 mg/dL lower with nettle, but no significant change in HbA1c, insulin or insulin resistance, and results varied widely between trials. A later pooling of 13 trials did find lower HbA1c. Neither analysis was limited to leaf preparations.
Triglycerides and HDL cholesterol in a small trial
In 50 women over 50 with type 2 diabetes taking metformin and glibenclamide, 5 mL of a water and alcohol extract of nettle aerial parts three times daily for 8 weeks lowered fasting glucose, triglycerides and the liver enzyme ALT, and raised HDL cholesterol, compared with placebo. It is a single trial that has not been repeated.
Minor joint pain as a traditional use
The European Medicines Agency accepts nettle leaf as a traditional herbal medicine for minor joint pain, based on long use. Its reviewers judged the clinical studies poor and not convincing; most were open studies without a control group. In an open trial in 40 people with an arthritis flare, stewed nettle plus low-dose diclofenac did about as well as a 4 times higher diclofenac dose, with no placebo group.
Joint scores with nettle-containing blends
Two placebo-controlled trials in people with knee or hip osteoarthritis tested blends. A fish oil, vitamin E, zinc and nettle capsule cut painkiller use and WOMAC scores in 81 people, but outside reviewers rated the trial at high risk of bias. A rosehip, nettle leaf and devil's claw drink lowered knee pain scores in 92 people. Both were industry-funded, and neither can show what nettle adds.
Urine flow as a traditional use
The EU monograph also lists nettle leaf as a traditional remedy to increase urine and flush the urinary tract, alongside other care for minor urinary complaints, for 2 to 4 weeks. EU reviewers found no study of the leaf's own diuretic effect and relied on data for the whole herb. It should not be used where reduced fluid intake is advised, such as severe heart or kidney disease.
Mechanism of action
Lower cytokine release from blood samples
In 20 healthy volunteers who took a nettle leaf extract (IDS 23) for 21 days, blood drawn afterward released 24% less TNF-α and 39% less IL-1β when stimulated in the lab, while resting cytokine levels stayed below detection. There was no placebo group, and this is a lab measure, not a symptom outcome.
Blood sugar effects in laboratory and animal work
Leaf extracts have shown insulin-releasing, PPARγ-activating and alpha-glucosidase-blocking effects in laboratory studies. In rats, an injected leaf fraction raised blood insulin and lowered blood sugar, but EU reviewers judged that result not relevant to the doses and preparations people take by mouth.
Flavonoids, minerals and vitamin K
The leaf contains about 1 to 2% flavonoids, caffeic acid esters, silicates and minerals such as potassium and calcium. Published vitamin K contents of 0.16 to 0.64 mg per 100 g mean that 15 g of leaf supplies roughly 24 to 96 µg of vitamin K, a small amount next to medical vitamin K doses.
Clinical trials
Randomized, double-blind, placebo-controlled trial of nettle leaf extract, one 500 mg capsule every 8 hours for 3 months, added to conventional oral glucose-lowering drugs. EU reviewers later noted the extract was made with 70% ethanol, unlike the preparations in the EU monograph. (Kianbakht et al. 2013, Clin Lab)
92 adults in Iran with advanced type 2 diabetes needing insulin therapy (46 nettle, 46 placebo).
Compared with placebo, the extract lowered fasting glucose (p < 0.001), 2-hour post-meal glucose (p = 0.009) and HbA1c (p = 0.006), with no significant effect on creatinine, the liver enzymes SGOT and SGPT, or blood pressure. The abstract does not give the size of the changes, and EU reviewers noted that the background diabetes drugs were not specified.
Double-blind, randomized, placebo-controlled trial of 5 mL of a hydro-alcoholic extract of nettle aerial parts or placebo three times daily after meals for 8 weeks, alongside metformin and glibenclamide. The extract was supplied by a company; the authors declared no conflicts of interest. (Amiri Behzadi et al. 2016, Avicenna J Phytomed)
50 women over age 50 with type 2 diabetes in Iran.
Compared with placebo, fasting glucose, triglycerides and ALT fell, and HDL cholesterol, nitric oxide and the antioxidant enzyme SOD rose. LDL cholesterol and AST were also measured, and the abstract reports no change in them. A small single trial.
Randomized, double-blind, placebo-controlled trial of capsules each holding 200 mg nettle leaf extract, 200 mg silymarin and 200 mg olibanum gum, one capsule three times daily before meals for 90 days, added to oral glucose-lowering drugs. Funded by academic grants; no conflicts declared. (Khalili et al. 2017, J Evid Based Complementary Altern Med)
60 adults aged 40 to 60 with type 2 diabetes, fasting glucose 150 to 180 mg/dL and HbA1c 7.5% to 8.5% (30 per group).
After 3 months, fasting glucose (124.7 vs 147.8 mg/dL), HbA1c (6.56% vs 7.64%) and triglycerides were lower with the blend than with placebo; post-meal glucose, cholesterol and blood pressure did not differ. No adverse events were reported. As a three-herb blend, it cannot show the effect of nettle alone.
Randomized, double-blind, placebo-controlled trial of a freeze-dried Urtica dioica preparation for one week, assessed with daily symptom diaries and a global rating at the follow-up visit. The abstract does not state the plant part or dose; a later paper by other authors calls it a leaf extract. (Mittman 1990, Planta Med)
98 people with allergic rhinitis; 69 completed the study.
Nettle was rated higher than placebo in the global assessments, but only slightly higher in the daily symptom diaries. The abstract gives no dose or statistics, and 29 of 98 participants did not finish. Because the plant part is not stated, it cannot be confirmed as a leaf trial.
Open, randomized pilot study comparing 50 mg diclofenac plus 50 g of stewed nettle daily with 200 mg diclofenac alone; both groups also took the stomach-protecting drug misoprostol. No placebo group. (Chrubasik et al. 1997, Phytomedicine)
40 people with an acute flare of chronic joint disease (acute arthritis); 37 completed.
CRP and joint symptom scores improved by about 70% in both groups. Without a placebo or a low-dose diclofenac alone arm, the study cannot show what nettle added. The paper calls the material nettle herb, and EU reviewers set it aside on that basis. Minor side effects included bloating in 3 nettle users.
Randomized, double-blind, placebo-controlled trial of Phytalgic, three capsules a day for 3 months. Funded by the maker, Laboratoires Phythea; one author was a Phythea employee. (Jacquet et al. 2009, Arthritis Res Ther)
81 adults with knee or hip osteoarthritis who regularly used NSAIDs or other painkillers.
After 3 months, painkiller use was 6.5 vs 16.5 paracetamol-equivalent tablets a week and NSAID use 0.4 vs 1.0 daily doses with the blend vs placebo, and WOMAC pain, stiffness and function scores were much lower. Outside reviewers called the effect unusually large and the risk of bias high, citing registration after the trial ended and a fish-oil taste that could reveal treatment. The nettle amount is not stated in the abstract.
Randomized, double-blind, placebo-controlled trial of 40 mL a day of MA212 (Rosaxan), rosehip purée and juice concentrate with nettle leaf extract, devil's claw root extract and vitamin D, sold in the EU as a food for special medical purposes. Two authors planned and analyzed the study for a company affiliated with the sponsor. (Moré et al. 2017, Planta Med)
92 randomized patients with knee osteoarthritis (gonarthritis); 46 took MA212 and 44 took placebo.
WOMAC pain scores fell by 29.87 points on MA212 vs 10.23 on placebo (p < 0.001), and physical and mental quality of life improved more; painkiller use showed only a trend toward reduction. MA212 was well tolerated. With three plant ingredients plus vitamin D, the nettle contribution cannot be separated.