Ginkgo biloba is a tree whose leaves are made into one of the best-selling herbal extracts in the world. It is marketed mainly for memory and “brain health,” and also for circulation, tinnitus and many other conditions (NCCIH). Most clinical research used one standardized leaf extract, EGb 761, often at 120 mg twice daily.
The single most important fact: the largest trials do not support the main claims. In two multi-year prevention trials with about 5,900 older adults combined, ginkgo did not reduce the risk of dementia or Alzheimer’s disease. A meta-analysis also found no measurable cognitive benefit in healthy people. In the US it is sold as a dietary supplement, not an approved drug. In the EU, a specific dry extract is recognized as an herbal medicine for age-related cognitive impairment and mild dementia.
This page summarizes what regulators, the large randomized trials and systematic reviews report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Type | Herbal leaf extract (Ginkgo biloba L., folium) |
| Main active groups | Flavonol glycosides and terpene lactones (ginkgolides A, B, C and bilobalide) |
| Standardized extract (Ph. Eur.) | 22–27% flavonoids, 5.4–6.6% terpene lactones, under 5 ppm ginkgolic acids |
| Route | Oral |
| Studied / EU monograph dose | 240 mg/day of dry extract (EU: 120–240 mg per dose); large trials used 120 mg twice daily |
| Half-life (terpene lactones) | ≈ 2–11 h depending on compound and formulation |
| US status | Dietary supplement; not FDA-approved for any condition |
| EU status | Herbal medicine for age-associated cognitive impairment and quality of life in mild dementia (ATC N06DX02) |
| Cancer classification | IARC Group 2B (“possibly carcinogenic to humans”), based on rodent studies |
| WADA | Not named on the 2026 Prohibited List |
What it is
Ginkgo biloba is one of the oldest living tree species. It originated in China and is now planted worldwide (IARC Monographs Vol. 108). Its leaves are the part used in supplements and herbal medicines. Its seeds are eaten as food in East Asia, but they contain a different toxin (see below).
The leaf extract contains two main groups of compounds:
- Flavonol glycosides, mainly glycosides of quercetin, kaempferol and isorhamnetin.
- Terpene lactones: ginkgolides A, B and C and bilobalide, which are found only in ginkgo.
The leaf also contains ginkgolic acids, which are allergenic alkylphenols. Pharmaceutical-grade extracts remove most of them.
Standardized extract versus other products
“Ginkgo” on a label can mean very different things. The EU herbal monograph covers a refined dry extract made with 60% acetone, at a drug-to-extract ratio of 35–67:1 (EMA monograph, 2015). That extract must meet the European Pharmacopoeia specification (Kulić et al., Front Pharmacol 2022):
| Component | Ph. Eur. “refined and quantified” extract |
|---|---|
| Flavonoids (as flavone glycosides) | 22.0–27.0% |
| Terpene lactones, total | 5.4–6.6% |
| Ginkgolides A, B, C | 2.8–3.4% |
| Bilobalide | 2.6–3.2% |
| Ginkgolic acids | Under 5 ppm |
The US Pharmacopeia uses a similar flavonoid range (22–27%) but allows 5.4–12% terpene lactones (IARC Monographs Vol. 108). IARC notes that pharmacopeial standards are mandatory for registered drug products but not for dietary supplements or foods. EGb 761, the extract used in GEM and GuidAge, is a proprietary extract made to the European specification. The Kulić review describing it was written by employees of its manufacturer.
Mechanism
The EU monograph states that “the exact mechanism is not known” (EMA monograph). It lists these human pharmacology findings:
- increased EEG vigilance in older people;
- lower blood viscosity;
- better blood flow in specific brain areas in healthy men aged 60–70;
- reduced platelet aggregation;
- dilation of forearm blood vessels.
Laboratory studies also describe antioxidant activity and antagonism of platelet-activating factor (IARC Monographs Vol. 108). These are cell and animal findings and do not by themselves show a clinical benefit.
Pharmacokinetics
The best-characterized compounds are the terpene lactones. In 12 young healthy volunteers given EGb 761 as an oral solution, absolute bioavailability was 80% for ginkgolide A, 88% for ginkgolide B and 79% for bilobalide (Fourtillan et al., Therapie 1995). Food did not change total exposure but delayed the peak.
| Compound | Half-life, solution (fasting) | Half-life, tablets (EU monograph) |
|---|---|---|
| Ginkgolide A | 4.5 h | 3–4 h |
| Ginkgolide B | 10.6 h | 4–6 h |
| Bilobalide | 3.2 h | 2–3 h |
Solution values from Fourtillan 1995; tablet values from the EMA monograph.
These short half-lives are consistent with the twice-daily dosing used in most trials. The flavonoids are extensively metabolized. After oral dosing in humans, quercetin and kaempferol appear in urine mainly as glucuronide conjugates (IARC Monographs Vol. 108).
The product matters. A single-dose study compared three ginkgo preparations at their maximum daily dose (Woelkart et al., Phytother Res 2010):
| Product | Bilobalide peak | Ginkgolide A peak | Ginkgolide B peak |
|---|---|---|---|
| Tincture | 3.53 ng/mL | 3.62 ng/mL | 1.38 ng/mL |
| Fresh-plant extract tablets | 11.68 ng/mL | 7.36 ng/mL | 4.18 ng/mL |
| EGb 761 tablets | 26.85 ng/mL | 16.44 ng/mL | 9.99 ng/mL |
Regulatory status
- European Union. The EMA’s herbal committee recognizes the refined dry extract as a “well-established use” herbal medicine for improving age-associated cognitive impairment and quality of life in mild dementia. The labeled dose is 240 mg/day, for at least 8 weeks. If there is no improvement after 3 months, the doctor should check whether treatment is still justified (EMA monograph). Powdered leaf is registered separately as a “traditional use” product for heavy legs and cold hands and feet, based only on long-standing use.
- United States. Ginkgo is sold as a dietary supplement under the 1994 Dietary Supplement Health and Education Act. It does not need FDA approval before sale, and labels may not claim to treat or prevent disease (IARC Monographs Vol. 108; NCCIH).
- Sport. Ginkgo is not named on the WADA 2026 Prohibited List. The contamination issues described below still apply to any supplement.
What the research shows
The US National Center for Complementary and Integrative Health summarizes the evidence bluntly: ginkgo “has not been shown to be effective for any of the conditions for which it has been studied” (NCCIH).
Preventing dementia
Two large, long, placebo-controlled trials tested EGb 761 at 120 mg twice daily:
| Trial | Participants | Follow-up | Result |
|---|---|---|---|
| GEM, US (DeKosky et al., JAMA 2008) | 3,069 adults aged 75+ with normal cognition or mild cognitive impairment | Median 6.1 years | All-cause dementia HR 1.12 (95% CI 0.94–1.33); Alzheimer’s HR 1.16 (95% CI 0.97–1.39) |
| GuidAge, France (Vellas et al., Lancet Neurol 2012) | 2,854 adults aged 70+ with memory complaints | 5 years | Probable Alzheimer’s HR 0.84 (95% CI 0.60–1.18) |
In GEM, 277 people on ginkgo and 246 on placebo developed dementia, or 3.3 vs 2.9 cases per 100 person-years. In the 482 participants who started with mild cognitive impairment, ginkgo did not slow progression to dementia (HR 1.13, 95% CI 0.85–1.50). GuidAge recorded 1.2 vs 1.4 Alzheimer’s cases per 100 person-years, which was not significant. GuidAge was funded by Ipsen.
A further GEM analysis looked at the rate of cognitive decline in memory, attention, visuospatial skills, language and executive function. Annual decline was the same on ginkgo and placebo in every domain. There was also no subgroup by age, sex, education or APOE4 status that benefited (Snitz et al., JAMA 2009).
Treating existing dementia
Results here are mixed, and they depend heavily on which trials are pooled.
- Cochrane review (2009). It included 36 trials, most of them small and under 3 months long. Across the nine trials of 6 months (2,016 patients), the results were “inconsistent and unreliable” (Birks and Grimley Evans, Cochrane 2009). Three of the four most recent trials found no difference from placebo, while one found a very large benefit.
- EGb 761 meta-analysis (2015). It pooled 9 trials of 22–26 weeks with 2,561 patients. Cognition, daily-living scores and clinician global ratings favored EGb 761, mainly at 240 mg/day and mainly in patients with neuropsychiatric symptoms (Tan et al., J Alzheimers Dis 2015). In the Alzheimer’s subgroup, the effect was no larger than in the whole group.
NCCIH describes this as a possible modest benefit for dementia symptoms at relatively high doses, with inconsistent evidence (NCCIH).
Cognition in healthy people
The “nootropic” use has the weakest support. A meta-analysis of randomized trials in healthy people found effects that were close to zero and not significant (Laws et al., Hum Psychopharmacol 2012):
| Domain | Trials | Participants | Effect size (d, 95% CI) |
|---|---|---|---|
| Memory | 13 | 1,132 | −0.04 (−0.17 to 0.07) |
| Executive function | 7 | 534 | −0.05 (−0.17 to 0.05) |
| Attention | 8 | 910 | −0.08 (−0.21 to 0.02) |
The effect sizes were not related to age, trial length, daily dose or total dose.
Circulation (intermittent claudication)
Intermittent claudication is leg pain on walking caused by narrowed arteries. A Cochrane review of 14 trials (739 participants) pooled 11 placebo-controlled trials (477 participants). Ginkgo increased the absolute claudication distance by about 64.5 m on a flat treadmill at 3.2 km/h (95% CI −1.8 to 130.7 m), which was not statistically significant (Nicolaï et al., Cochrane 2013). The authors concluded there is no evidence of a clinically significant benefit, and that publication bias probably inflated even this estimate.
Tinnitus
A 2022 Cochrane review included 12 trials (1,915 participants), most at high or unclear risk of bias. Ginkgo “may have little to no effect” on tinnitus severity at 3–6 months: mean difference −1.35 points on a 0–100 scale (95% CI −8.26 to 5.55), with very low certainty (Sereda et al., Cochrane 2022).
Altitude sickness and exercise
The largest altitude trial randomized 614 trekkers on the route to Everest base camp to ginkgo, acetazolamide, both, or placebo (Gertsch et al., BMJ 2004):
| Group | Acute mountain sickness |
|---|---|
| Placebo | 34% |
| Ginkgo | 35% |
| Acetazolamide | 12% |
| Ginkgo + acetazolamide | 14% |
Ginkgo did not differ from placebo on any outcome.
Exercise data are minimal. In one small trial, 18 physically active young men took 160 mg/day of a standardized extract or placebo (9 per group) for 6 weeks (Sadowska-Krępa et al., Nutrients 2017). The authors described “marginal” improvements in VO₂max and blood antioxidant markers. No adequately sized trials show that ginkgo improves strength, muscle growth or recovery.
Side effects and risks
Common side effects
In the trials, ginkgo leaf extract is generally well tolerated. In the Cochrane dementia review, adverse events were no more common than on placebo (Birks and Grimley Evans, Cochrane 2009). The EU monograph lists these effects (EMA monograph):
| Frequency | Effects |
|---|---|
| Very common | Headache |
| Common | Dizziness; diarrhea, abdominal pain, nausea, vomiting |
| Frequency not known | Bleeding (eye, nose, brain, gut); allergic skin reactions; allergic shock |
Bleeding
The concern comes from ginkgo’s effect on platelets and from case reports. Controlled data are more reassuring, with one signal that has not been resolved:
- Meta-analysis of 18 RCTs (1,985 adults). Standardized extract lowered blood viscosity. It had no significant effect on ADP-induced platelet aggregation, fibrinogen, aPTT or prothrombin time (Kellermann and Kloft, Pharmacotherapy 2011). The authors found no indication of higher bleeding risk.
- GEM safety data. Major bleeding occurred in 8.9% on ginkgo vs 9.2% on placebo (HR 0.97, 95% CI 0.77–1.23). Hemorrhagic strokes were 16 vs 8 (HR 1.97, 95% CI 0.84–4.61), which was not significant. The investigators said this “should be explored in future studies” (DeKosky et al., JAMA 2008).
- GuidAge. Strokes were 65 on ginkgo vs 60 on placebo (RR 1.12, 95% CI 0.77–1.63), and other hemorrhagic events did not differ (Vellas et al., Lancet Neurol 2012).
The EU monograph still advises stopping ginkgo 3–4 days before surgery. It says people with a bleeding disorder, or on anticoagulant or antiplatelet drugs, should use it only after consulting a doctor.
Drug interactions
The EU monograph lists these interactions (EMA monograph):
| Drug | What was reported |
|---|---|
| Anticoagulants and antiplatelets (warfarin, phenprocoumon, clopidogrel, aspirin, NSAIDs) | Effect may be influenced. Warfarin studies did not show an interaction, but monitoring is advised when starting, stopping or switching ginkgo products |
| Efavirenz (HIV drug) | Levels may fall through CYP3A4 induction; combination not recommended |
| Dabigatran | Ginkgo may inhibit intestinal P-glycoprotein and raise exposure; caution advised |
| Nifedipine | Peak levels up to doubled in some people, with dizziness and hot flushes |
Cancer findings in animals
The US National Toxicology Program gave a ginkgo leaf extract by stomach tube for 2 years to rats (100–1,000 mg/kg) and mice (200–2,000 mg/kg), 5 days a week (NTP TR-578, 2013):
- Mice: “clear evidence” of carcinogenic activity, from liver tumors: hepatocellular carcinoma and hepatoblastoma in males, and hepatocellular adenoma, carcinoma and hepatoblastoma in females.
- Rats: “some evidence,” from thyroid follicular cell tumors in both sexes.
The extract was also mutagenic in bacterial tests. Based largely on these studies, IARC classified Ginkgo biloba extract as possibly carcinogenic to humans (Group 2B). It found inadequate evidence in humans and sufficient evidence in experimental animals (IARC Monographs Vol. 108).
Context matters for both conclusions:
- The doses were far higher than human doses.
- The NTP extract contained 15.4% terpene lactones and 10.45 ppm ginkgolic acid, outside the European specification above.
- The EU monograph considers the rodent liver and thyroid tumors a rodent-specific, non-genotoxic response to high doses of liver-enzyme inducers, “not considered relevant to humans.”
In GEM, cancer hospitalizations were 162 on ginkgo vs 148 on placebo (HR 1.09, 95% CI 0.87–1.36). This was a secondary analysis, and IARC judged its statistical power for cancer to be low (IARC Monographs Vol. 108).
Seeds are toxic
Ginkgo seeds contain ginkgotoxin (4′-O-methylpyridoxine), a compound structurally related to vitamin B6 (IARC Monographs Vol. 108). NCCIH notes that fresh seeds are toxic when eaten. Serious effects have also been reported after eating roasted seeds or the crude plant (NCCIH). Reported cases of seed poisoning usually involve children with repeated seizures (Kajiyama et al., Pediatrics 2002). This hazard is separate from leaf extract.
Who should avoid it
The EU monograph identifies these groups:
- Pregnancy: a contraindication. Ginkgo may impair platelet aggregation, and the reproductive toxicity data are inadequate.
- Breastfeeding: use is not recommended because data are lacking.
- Under 18: no relevant indication.
- Epilepsy: further seizures “cannot be excluded.”
- Bleeding disorders, or anticoagulant and antiplatelet therapy: only after medical advice.
Quality and contamination
Adulteration of ginkgo products is well documented. A 2024 review of published testing pooled 533 ginkgo leaf samples and found 56.7% adulterated or mislabeled, the highest rate of the five herbs examined (Orhan et al., Nat Prod Rep 2024). A known method is adding cheaper material rich in rutin or other flavonoids, such as Japanese pagoda tree (Styphnolobium japonicum), to raise the apparent flavonoid content measured by standard assays (IARC Monographs Vol. 108; Kulić et al., Front Pharmacol 2022). In the 2024 review, products sold as licensed or registered herbal medicines had a lower risk of adulteration than those sold as dietary or food supplements.
Because most trials used one pharmaceutical-grade extract, results from GEM, GuidAge or the dementia meta-analyses may not apply to a given supplement.
Key takeaways
- No dementia prevention. Two trials with about 5,900 older adults followed for 5–6 years found no reduction in dementia or Alzheimer’s disease.
- No cognitive boost in healthy people. Pooled effects on memory, attention and executive function were near zero.
- Mixed results in existing dementia. Some pooled analyses of EGb 761 at 240 mg/day show modest benefit. Cochrane rated the evidence inconsistent, and the EU recognizes this one indication.
- Usually well tolerated, but interactions matter. Headache, dizziness and stomach upset are the common effects. Major bleeding did not rise in controlled trials, though GEM saw a non-significant excess of hemorrhagic strokes. The EU monograph advises caution with anticoagulants, efavirenz and surgery.
- Product quality varies widely. More than half of tested ginkgo samples were adulterated or mislabeled, and supplements do not have to meet pharmacopeial standards.
- No evidence for training or recovery. A large trial found no effect on altitude sickness, and one small exercise study reported only marginal results.
Sources
- Committee on Herbal Medicinal Products (HMPC). European Union herbal monograph on Ginkgo biloba L., folium. EMA/HMPC/321097/2012. European Medicines Agency; 2015. EMA.
- National Center for Complementary and Integrative Health. Ginkgo: usefulness and safety. NCCIH.
- IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Ginkgo biloba. In: Some drugs and herbal products. IARC Monogr Eval Carcinog Risks Hum. 2016;108:91–116. IARC.
- National Toxicology Program. Toxicology and carcinogenesis studies of Ginkgo biloba extract (CAS No. 90045-36-6) in F344/N rats and B6C3F1/N mice (gavage studies). Natl Toxicol Program Tech Rep Ser. 2013;(578):1–183. NTP; PubMed.
- Kulić Ž, Lehner MD, Dietz GPH. Ginkgo biloba leaf extract EGb 761® as a paragon of the product by process concept. Front Pharmacol. 2022;13:1007746. PubMed.
- Fourtillan JB, Brisson AM, Girault J, et al. Pharmacokinetic properties of Bilobalide and Ginkgolides A and B in healthy subjects after intravenous and oral administration of Ginkgo biloba extract (EGb 761) (article in French). Therapie. 1995;50(2):137–144. PubMed.
- Woelkart K, Feizlmayr E, Dittrich P, et al. Pharmacokinetics of bilobalide, ginkgolide A and B after administration of three different Ginkgo biloba L. preparations in humans. Phytother Res. 2010;24(3):445–450. PubMed.
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- 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):2663–2670. PubMed.
- 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):851–859. PubMed.
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- Nicolaï SP, Kruidenier LM, Bendermacher BL, et al. Ginkgo biloba for intermittent claudication. Cochrane Database Syst Rev. 2013;(6):CD006888. PubMed.
- Sereda M, Xia J, Scutt P, et al. Ginkgo biloba for tinnitus. Cochrane Database Syst Rev. 2022;11(11):CD013514. PubMed.
- Gertsch JH, Basnyat B, Johnson EW, et al. Randomised, double blind, placebo controlled comparison of ginkgo biloba and acetazolamide for prevention of acute mountain sickness among Himalayan trekkers: the prevention of high altitude illness trial (PHAIT). BMJ. 2004;328(7443):797. PubMed.
- Sadowska-Krępa E, Kłapcińska B, Pokora I, et al. Effects of six-week Ginkgo biloba supplementation on aerobic performance, blood pro/antioxidant balance, and serum brain-derived neurotrophic factor in physically active men. Nutrients. 2017;9(8):803. PubMed.
- 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. PubMed.
- Orhan N, Gafner S, Blumenthal M. Estimating the extent of adulteration of the popular herbs black cohosh, echinacea, elder berry, ginkgo, and turmeric - its challenges and limitations. Nat Prod Rep. 2024;41(10):1604–1621. PubMed.
- Kajiyama Y, Fujii K, Takeuchi H, Manabe Y. Ginkgo seed poisoning. Pediatrics. 2002;109(2):325–327. PubMed.
- World Anti-Doping Agency. The 2026 Prohibited List. WADA 2026 Prohibited List.