Home Ingredients Hibiscus (Roselle)
CardiovascularAntioxidantMetabolic Health

Hibiscus (Roselle)

Hibiscus sabdariffa
Evidence Level
Moderate
5 Clinical Trials
4 Documented Benefits
3/5 Evidence Score

Hibiscus, also called roselle or sour tea, is a tropical plant whose deep-red calyces are brewed into a tart, caffeine-free tea and sold as extracts. The calyces are rich in anthocyanins, mainly delphinidin-3-sambubioside and cyanidin-3-sambubioside, along with organic acids such as hibiscus acid and other polyphenols. Most human research looks at blood pressure. In a 6-week placebo-controlled trial in 65 adults with high-normal or mildly raised blood pressure, three cups of hibiscus tea a day lowered systolic pressure by 7.2 mm Hg, against 1.3 mm Hg with placebo, and two meta-analyses report average systolic drops of about 7 mm Hg. A 2022 meta-analysis also found a small drop in LDL cholesterol. Antioxidant and blood sugar findings are less consistent. People taking medicines should check with their prescriber, as hibiscus can affect blood pressure and some drugs.

Studied Dose Trials used 1.25 to 10 g of dried calyces brewed as tea per serving; the main US trial used 1.25 g in 240 mL three times a day for 6 weeks. One 4-week trial used 500 mg of calyx powder in capsules once a day.
Active Compound Anthocyanins (mainly delphinidin-3-sambubioside and cyanidin-3-sambubioside), organic acids including hibiscus acid, and other polyphenols.

Benefits

Supports Healthy Blood Pressure

In a 6-week placebo-controlled trial in 65 adults with high-normal or mildly raised blood pressure who took no blood pressure medicine, three cups of hibiscus tea a day lowered systolic pressure by 7.2 mm Hg versus 1.3 mm Hg with placebo; diastolic change did not differ. Meta-analyses report average systolic drops of about 7 mm Hg, larger in people with higher starting values.

Supported by Trial 1, Trial 2

Promotes Healthy Cholesterol Balance

A 2022 meta-analysis of 17 trials found hibiscus lowered LDL cholesterol by about 6.8 mg/dL compared with other teas and placebo, a small change at the edge of statistical significance. A 2025 umbrella review reported lower total and LDL cholesterol and higher HDL. In a 4-week trial in 40 adults with metabolic syndrome, 500 mg of calyx powder lowered triglycerides versus placebo.

Supported by Trial 3, Trial 4

Provides Antioxidant Activity

In a small open-label crossover study in 8 healthy volunteers, drinking a hibiscus extract raised the antioxidant capacity of the blood and lowered urinary malondialdehyde, a marker of oxidative damage, compared with water. In a 4-week placebo-controlled trial in 40 adults with metabolic syndrome, malondialdehyde did not change, so the effect in people is not settled.

Supported by Trial 4, Trial 1

Fasting Blood Sugar

A 2025 umbrella review, which re-analyzed trials from earlier meta-analyses (26 trials in all), reported lower fasting blood glucose with hibiscus. Single trials have been less consistent: in the 4-week placebo-controlled trial in adults with metabolic syndrome, fasting glucose and insulin did not change.

Supported by Trial 4, Trial 2

Mechanism of action

1

ACE Inhibition

Reviews list inhibition of angiotensin-converting enzyme (ACE), an enzyme that raises blood pressure, among the proposed explanations for the blood pressure effect. This comes mainly from laboratory and animal work.

2

Blood Vessel Relaxation

In laboratory and animal studies, hibiscus extracts relaxed blood vessels through pathways that depend on the vessel lining and by limiting calcium entry into vessel muscle. How much this explains the effect in people has not been measured directly.

3

Antioxidant Free-Radical Scavenging

Hibiscus anthocyanins scavenge free radicals in laboratory tests, and reviews propose that limiting the oxidation of LDL particles is one way they may support the heart and blood vessels. In people, antioxidant marker results have been mixed.

4

Mild Diuretic Action

A 2013 review found evidence that hibiscus acts as a mild diuretic, mostly in animal studies, while in most studies it did not change blood levels of sodium, potassium or other electrolytes.

Clinical trials

1
Hibiscus Tea in Adults with High-Normal Blood Pressure
PubMed

Randomized, double-blind, placebo-controlled trial; three 240 mL servings of brewed hibiscus tea a day for 6 weeks (McKay et al. 2010, J Nutr)

65 adults aged 30 to 70 with high-normal or mildly raised blood pressure, not taking blood pressure medicine

Systolic pressure fell 7.2 mm Hg with hibiscus tea versus 1.3 mm Hg with placebo (p = 0.030). Diastolic pressure did not differ from placebo (p = 0.160), and mean arterial pressure was borderline (p = 0.054). People with higher starting systolic pressure responded more.

2
Meta-Analysis of Hibiscus and Blood Pressure (2015)
PubMed

Systematic review and fixed-effect meta-analysis of randomized controlled trials (Serban et al. 2015, J Hypertens)

5 trials with 7 treatment arms and 390 participants

Hibiscus lowered systolic pressure by 7.58 mm Hg and diastolic pressure by 3.53 mm Hg on average compared with control, with larger effects in people with higher starting values. The authors call for further well-designed trials.

3
Meta-Analysis of Hibiscus and Heart Health Markers (2022)
PubMed

Systematic review and random-effects meta-analysis of randomized controlled trials (Ellis et al. 2022, Nutr Rev)

17 trials in adults

Compared with placebo, hibiscus lowered systolic pressure by 7.10 mm Hg, with very high variation between trials. LDL cholesterol fell by 6.76 mg/dL compared with other teas and placebo (p = 0.05).

4
Hibiscus Calyx Powder in Adults with Metabolic Syndrome
PubMed

Randomized, double-blind, placebo-controlled trial; 500 mg of calyx powder once a day for 4 weeks (Asgary et al. 2016, J Complement Integr Med)

40 adults with metabolic syndrome

Triglycerides (p = 0.044) and systolic pressure (p = 0.049) fell compared with placebo. Fasting glucose, insulin, cholesterol fractions, hs-CRP and malondialdehyde did not change significantly.

5
Sour Tea Versus Green Tea in Adults with Type 2 Diabetes
PubMed

Randomized trial without a placebo group; sour (hibiscus) tea or green tea three times a day for 4 weeks (Mozaffari-Khosravi et al. 2013, J Diet Suppl)

100 adults with type 2 diabetes and mildly raised blood pressure

Systolic and diastolic pressure fell in both groups (systolic 123.1 to 116.8 mm Hg with sour tea and 119.4 to 114.8 mm Hg with green tea). The abstract does not report a difference between the two teas.

Side effects and drug interactions

Common Potential side effects

Reviews of human trials describe hibiscus tea and extracts as generally well tolerated; a 2025 umbrella review found a small rise in the liver enzyme AST that it judged clinically insignificant, with no increase in adverse events.
A 2013 review notes liver enzyme changes at very high extract doses in research studies, so concentrated extracts are best kept to studied amounts.
Hibiscus can lower blood pressure, so people with low blood pressure should take care.
Not well studied in pregnancy or breastfeeding; ask your doctor before using medicinal amounts.

Important Drug interactions

Blood pressure medicines: hibiscus lowers blood pressure, so the effects may add up; check with your prescriber and do not change prescribed medicine on your own.
Chloroquine: in healthy men, taking chloroquine with karkadi, a hibiscus drink, cut the amount of drug absorbed by about 70% compared with water.
Hydrochlorothiazide and other diuretics: in rats, hibiscus extract given with hydrochlorothiazide increased urine output, and a 2013 review advised against combining them.
Acetaminophen (paracetamol): in 6 healthy men, a hibiscus drink taken before acetaminophen sped up the drug's elimination; absorption was unchanged.

More Cardiovascular Ingredients

Cardiovascular
Omega-3 Fatty Acids
Omega-3 fatty acids are polyunsaturated fats. EPA and DHA come from fish, krill and algae…
Cardiovascular
CoEnzyme Q10
Coenzyme Q10 (CoQ10) is a fat-soluble compound the body makes for itself. It carries elect…
Cardiovascular
Beetroot
Beetroot is a vegetable rich in dietary nitrate, which the body converts into nitric oxide…
Cardiovascular
Potassium
Potassium is the main mineral inside the body's cells and an essential nutrient for the el…

Explore Other Ingredients

Metabolic Health
Chromium
Chromium is a trace mineral found in meats, whole grains, fruits, vegetables, nuts, spices…
Metabolic Health
Inositol (Myo-Inositol)
Inositol is a naturally occurring sugar alcohol that acts as a secondary messenger in insu…
Metabolic Health
GlucoVantage® (Dihydroberberine)
GlucoVantage® is NNB Nutrition's branded dihydroberberine (DHB), a reduced form of berberi…

Frequently asked questions about Hibiscus (Roselle)

What is hibiscus used for?

Hibiscus is a tart, ruby-red flower enjoyed as a tea and studied mainly for supporting healthy blood pressure. It is rich in anthocyanin antioxidants and is a popular caffeine-free beverage.

Does hibiscus help with blood pressure?

Hibiscus tea has trial evidence for supporting healthy blood pressure, especially in people whose readings are mildly raised. In the main US trial, three cups a day for 6 weeks lowered systolic pressure by about 7 mm Hg, and meta-analyses report similar average drops. It is one of the better-studied herbal teas for this.

How much hibiscus should I drink?

Studies often use about 2 to 3 cups of hibiscus tea per day, or standardized extracts; follow product labeling. It has a pleasant tart, cranberry-like flavor.

Is hibiscus safe?

Hibiscus is generally well tolerated as a tea. Because it can lower blood pressure, people on blood pressure medicine should check with their prescriber, and it changes how chloroquine and acetaminophen are absorbed or cleared. It has not been well studied in pregnancy or breastfeeding, so ask your doctor before using medicinal amounts.

What is Hibiscus?

Hibiscus, also called roselle or sour tea, is a tropical plant whose deep-red calyces are brewed into a tart, caffeine-free tea and sold as extracts. The calyces are rich in anthocyanins, mainly delphinidin-3-sambubioside and cyanidin-3-sambubioside, along with organic acids such as hibiscus acid and other polyphenols.

What is the recommended dosage of Hibiscus?

The clinically studied dose is Trials used 1.25 to 10 g of dried calyces brewed as tea per serving; the main US trial used 1.25 g in 240 mL three times a day for 6 weeks. One 4-week trial used 500 mg of calyx powder in capsules once a day. Always follow the product label and check with a healthcare provider for personal advice.

Is Hibiscus safe, and does it have side effects?

For most healthy adults, Hibiscus is well tolerated at studied doses. Reported effects can include: Reviews of human trials describe hibiscus tea and extracts as generally well tolerated; a 2025 umbrella review found a small rise in the liver enzyme AST that it judged clinically insignificant, with no increase in adverse events. It may also interact with some medications. Hibiscus 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 Hibiscus interact with any medications?

Possible interactions include: Blood pressure medicines: hibiscus lowers blood pressure, so the effects may add up; check with your prescriber and do not change prescribed medicine on your own. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Hibiscus?

NutraSmarts rates the evidence for Hibiscus as Moderate (3 out of 5). It is backed by 5 clinical trials and 10 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(10 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. McKay DL, Chen CY, Saltzman E, Blumberg JB. Hibiscus sabdariffa L. tea (tisane) lowers blood pressure in prehypertensive and mildly hypertensive adults. J Nutr. 2010;140(2):298-303. doi: 10.3945/jn.109.115097.PubMedUsed to support: Randomized, double-blind, placebo-controlled trial in 65 adults aged 30 to 70 with high-normal or mildly raised blood pressure: three servings a day of hibiscus tea for 6 weeks lowered systolic pressure by 7.2 mm Hg versus 1.3 mm Hg with placebo; diastolic pressure did not differ from placebo.
  2. Serban C, Sahebkar A, Ursoniu S, Andrica F, Banach M. Effect of sour tea (Hibiscus sabdariffa L.) on arterial hypertension: a systematic review and meta-analysis of randomized controlled trials. J Hypertens. 2015;33(6):1119-27. doi: 10.1097/HJH.0000000000000585.PubMedUsed to support: Meta-analysis of 5 randomized trials (390 participants): hibiscus lowered systolic pressure by 7.58 mm Hg and diastolic pressure by 3.53 mm Hg compared with control, with larger effects at higher starting values.
  3. Hopkins AL, Lamm MG, Funk JL, Ritenbaugh C. Hibiscus sabdariffa L. in the treatment of hypertension and hyperlipidemia: a comprehensive review of animal and human studies. Fitoterapia. 2013;85:84-94. doi: 10.1016/j.fitote.2013.01.003.PubMedUsed to support: Review of animal and human studies: describes hibiscus anthocyanins and hibiscus acid, a mild diuretic effect with little change in electrolytes, possible liver effects at very high doses, an animal herb-drug interaction with hydrochlorothiazide, and trial doses of 1.25 to 10 g of calyces per serving.
  4. Mozaffari-Khosravi H, Ahadi Z, Barzegar K. The effect of green tea and sour tea on blood pressure of patients with type 2 diabetes: a randomized clinical trial. J Diet Suppl. 2013;10(2):105-15. doi: 10.3109/19390211.2013.790333.PubMedUsed to support: Randomized trial in 100 adults with type 2 diabetes and mildly raised blood pressure comparing sour (hibiscus) tea with green tea three times a day for 4 weeks: systolic and diastolic pressure fell in both groups; there was no placebo group.
  5. Ellis LR, Zulfiqar S, Holmes M, Marshall L, Dye L, Boesch C. A systematic review and meta-analysis of the effects of Hibiscus sabdariffa on blood pressure and cardiometabolic markers. Nutr Rev. 2022;80(6):1723-1737. doi: 10.1093/nutrit/nuab104.PubMedUsed to support: Meta-analysis of 17 randomized trials in adults: hibiscus lowered systolic pressure by 7.10 mm Hg compared with placebo, with large variation between trials, and lowered LDL cholesterol by 6.76 mg/dL compared with other teas and placebo.
  6. Norouzzadeh M, Hasan Rashedi M, Azizi MH, Teymoori F, Maghsoomi Z, Shidfar F. Efficacy and safety of Hibiscus sabdariffa in cardiometabolic health: An overview of reviews and updated dose-response meta-analysis. Complement Ther Med. 2025;89:103135. doi: 10.1016/j.ctim.2025.103135.PubMedUsed to support: Umbrella review and meta-analysis of 26 randomized trials with 1797 participants: hibiscus lowered systolic and diastolic blood pressure in a dose-dependent way, lowered total and LDL cholesterol and fasting glucose and raised HDL; a small, clinically insignificant rise in AST was seen without more adverse events.
  7. Asgary S, Soltani R, Zolghadr M, Keshvari M, Sarrafzadegan N. Evaluation of the effects of roselle (Hibiscus sabdariffa L.) on oxidative stress and serum levels of lipids, insulin and hs-CRP in adult patients with metabolic syndrome: a double-blind placebo-controlled clinical trial. J Complement Integr Med. 2016;13(2):175-80. doi: 10.1515/jcim-2015-0030.PubMedUsed to support: Double-blind placebo-controlled trial in 40 adults with metabolic syndrome: 500 mg of calyx powder a day for 4 weeks lowered triglycerides and systolic pressure versus placebo; glucose, insulin, other lipids, hs-CRP and malondialdehyde did not change significantly.
  8. Frank T, Netzel G, Kammerer DR, Carle R, Kler A, Kriesl E, Bitsch I, Bitsch R, Netzel M. Consumption of Hibiscus sabdariffa L. aqueous extract and its impact on systemic antioxidant potential in healthy subjects. J Sci Food Agric. 2012;92(10):2207-18. doi: 10.1002/jsfa.5615.PubMedUsed to support: Randomized, open-label crossover study in 8 healthy volunteers: a hibiscus water extract raised plasma antioxidant capacity (FRAP) and lowered urinary malondialdehyde excretion compared with water.
  9. Mahmoud BM, Ali HM, Homeida MM, Bennett JL. Significant reduction in chloroquine bioavailability following coadministration with the Sudanese beverages Aradaib, Karkadi and Lemon. J Antimicrob Chemother. 1994;33(5):1005-9. doi: 10.1093/jac/33.5.1005.PubMedUsed to support: Pharmacokinetic study in healthy men: taking 600 mg chloroquine with karkadi (hibiscus) drink lowered chloroquine exposure (AUC 2.16 versus 7.52 mg.h/L with water) and peak level.
  10. Kolawole JA, Maduenyi A. Effect of zobo drink (Hibiscus sabdariffa water extract) on the pharmacokinetics of acetaminophen in human volunteers. Eur J Drug Metab Pharmacokinet. 2004;29(1):25-9. doi: 10.1007/BF03190570.PubMedUsed to support: Study in 6 healthy men: zobo (hibiscus) drink taken before 1 g acetaminophen did not change its absorption but sped up its elimination, with an 11.69% rise in total clearance.