Ginkgo biloba

The grades below are for healthy adults, and for long-term cognitive change in older adults without dementia. Our evidence grading method explains what each grade requires.

Does ginkgo improve memory in healthy adults?

Pooled trials found no benefit. A 2012 meta-analysis (a study that combines the results of many trials) included 13 randomized controlled trials with memory data from 1,132 healthy participants, and the effect size was non-significant and close to zero (d = -0.04, 95% CI -0.17 to 0.07) [1]. Effect sizes were not related to participant age, trial length, daily dose, total dose or sample size [1].

An earlier systematic review of 15 randomized, placebo-controlled, double-blind trials in healthy people under 60 reached the same view: it found no convincing evidence of a robust positive effect on any aspect of cognitive function after either single doses or longer use [2]. Several of the included studies had methodological flaws [2].

In a six-week randomized, double-blind, placebo-controlled trial, 230 community-dwelling adults older than 60 took ginkgo 40 mg three times a day or a matching placebo [3]. There were no significant differences between groups on any outcome measure, including learning and memory tests, and the ginkgo group did not differ in self-reported memory or in ratings by spouses, friends and relatives [3]. That trial was supported by a US National Institute on Aging grant [3].

Three trials report narrower positive results. In a 6-week trial of the extract EGb 761 (240 mg once daily) in 188 healthy adults aged 45-56, the ginkgo group recalled more appointments on a free-recall task, but showed no advantage on a second everyday memory test of recognizing a driving route [7]. In a 12-week placebo-controlled trial of 120 mg a day, older adults (55-79) improved on longer-term memory measured by associational learning tasks (d = 0.52, p = 0.04) and showed no statistically significant difference on any other measure [4]. In the student trial, a single 120 mg dose also improved a pattern-recognition memory task 4 hours later, but 6 weeks of daily use had no significant effect [6]. Against the pooled evidence, these are isolated findings.

Does ginkgo improve attention?

Evidence is mixed for single doses, and pooled results show no significant effect. In the 2012 meta-analysis, attention data from 8 randomized trials (910 participants) gave an effect size of d = -0.08 (95% CI -0.21 to 0.02), which was not statistically significant [1]. A 2026 network meta-analysis of 29 randomized trials (2,107 healthy adults) that compared ginkgo, bacopa and placebo found no significant differences in sustained attention, selective attention or processing speed [8]. Its authors note that the lack of direct comparisons may limit the strength of the evidence [8].

The positive signals come from small, short studies. In a double-blind crossover trial (each person took every treatment in turn) of 20 healthy young volunteers, single doses of 240 mg and 360 mg of a standardized extract (GK501, Pharmaton SA) improved a "speed of attention" score, evident at 2.5 hours and still present at 6 hours, compared with placebo [5]. The same trial found a number of time- and dose-specific changes, both positive and negative, on other measures [5]. In healthy university students, a single 120 mg dose improved a sustained-attention task tested 4 hours later, but 6 weeks of 120 mg a day had no significant effect on any cognitive test [6]. The authors suggested tolerance develops in young, healthy people; the trial was funded by the Dunhill Medical Trust, with study product donated by Lichtwer Pharma UK [6].

A systematic review points to study design: it notes that acute studies often measured many outcomes and reported positive effects at particular time points and doses that were either not replicated or directly contradicted by other studies [2].

Does ginkgo improve executive function?

Across 7 randomized trials with 534 healthy participants, the pooled effect was d = -0.05 (95% CI -0.17 to 0.05), close to zero and not significant [1]. In the student trial, neither a single dose nor 6 weeks of ginkgo changed planning or mental flexibility [6]. A 12-week trial of 120 mg a day in 104 young adults found no statistically significant effect on any measure, including executive function [4].

Does ginkgo slow cognitive change with age?

The largest long-term trial found no difference. The Ginkgo Evaluation of Memory (GEM) study was a randomized, double-blind, placebo-controlled trial of 3,069 community-dwelling adults aged 72 to 96, with a median follow-up of 6.1 years [9]. Participants took 120 mg of extract twice daily or an identical-looking placebo [9]. Annual rates of change in test scores did not differ between the ginkgo and placebo groups in any domain, including memory, attention, visuospatial skills, language and executive function [9]. GEM was funded by the US National Institute on Aging and the National Center for Complementary and Integrative Health and registered (NCT00010803), with study product (EGb 761 and placebo) donated by Schwabe Pharmaceuticals, which had no role in the study's design, analysis or approval but was sent the manuscript to check product facts [9].

What about people with diagnosed cognitive problems?

These results may not apply to healthy adults. A 2026 Cochrane review included 82 randomized trials with 10,613 participants; only four studies were at low risk of bias in all domains [10]. In people with diagnosed mild cognitive impairment (a clinical population), it found ginkgo probably has little or no effect at six months on global status, cognition or daily activities [10]. In people with diagnosed dementia (a clinical population), it found there may be small to moderate benefits at six months, with low-certainty evidence [10].

Other outcomes studied

Long-term use in young adults: in the student trial, 6 weeks of daily ginkgo produced no statistically significant change in mood or cognition [6], and a 12-week trial in young adults found no significant effect on any measure [4]. Mood in healthy adults: the same trials found no significant effect on mood ratings [4][6].

In adults and children with tinnitus (a clinical population), a 2022 Cochrane review of 12 trials (1,915 participants) found uncertainty about any benefit compared with placebo, and most included trials had a high or unclear risk of bias [11].

In a pharmacokinetic study (how the body absorbs and clears a substance) in 12 healthy volunteers, the peak blood level of ginkgolide B came 2.3 hours after a dose, whether the extract was given as 80 mg once daily or 40 mg twice daily [16].

Form may matter. In one single-dose study of three products, median peak blood levels of bilobalide after each product's maximum daily dose were 3.53 ng/mL for a tincture, 11.68 ng/mL for fresh-plant extract tablets and 26.85 ng/mL for EGb 761 tablets [17]. Health Canada requires licensed products to be tested for ginkgolic acids, at not more than 5 ppm [21].

For most adults, NCCIH describes ginkgo leaf extracts as likely to be safe when taken by mouth in moderate amounts, and notes they have been used in research lasting as long as 6 years [18]. NCCIH lists dizziness, gastrointestinal symptoms and headache as the most common side effects [18]. EMA reports that headache was the most common side effect in dementia use, seen in more than 1 patient in 10 [23].

In pooled trials in clinical populations, side effects were usually similar to placebo [10]. The 2026 Cochrane review found probably little or no difference in adverse events at up to 12 months in people with dementia, and little or no difference in serious adverse events in people with mild cognitive impairment (high-certainty evidence) [10]. It also found that, in one study of people with subjective cognitive complaints, the risk of adverse events at three months may be higher with ginkgo [10].

Bleeding is the caution regulators name [21][23]. EMA reports that bleeding in the eye, nose, brain or gut has been reported with ginkgo leaf medicines [23], and MSKCC lists case reports of spontaneous bleeding, including hematomas [19]. Pooled clotting tests are more reassuring: a meta-analysis of 18 randomized trials (1,985 adults, 87% of them patients and 13% healthy volunteers) found no significant effect on ADP-induced platelet aggregation and concluded that these laboratory measures did not indicate a higher bleeding risk with standardized extracts [12]. A Cochrane review in people with tinnitus found ginkgo may make little to no difference to the risk of bleeding or seizures, with no serious adverse effects in either group (low-certainty evidence) [11].

MSKCC also lists several case reports of low blood sodium, which returned to normal after ginkgo was stopped [19].

Seeds are a separate risk. Fresh ginkgo seeds are toxic when eaten, and serious side effects have occurred with roasted seeds or the crude plant [18]; a toxicology review also covers human case reports caused by seeds or leaves [15].

LiverTox, the NIH database on drug-induced liver injury, says ginkgo has not been implicated in causing liver injury and rates it an unlikely cause of clinically apparent liver injury (likelihood score E); the entry was last updated in 2018 [25].

Animal findings: in 2-year studies in rodents, the US National Toxicology Program found clear evidence of carcinogenic activity of one ginkgo leaf extract in mice, based on more liver tumors (hepatocellular carcinoma and hepatoblastoma), and IARC classifies ginkgo leaf extract as a possible human carcinogen (Group 2B) [15]. These are animal results, reported in a review funded through the FDA intramural program [15].

Health Canada's monograph says not to use ginkgo products if taking blood thinners or other health products that affect blood clotting [21]. EMA advises that people who tend to bleed or who use blood-thinning medicines should use ginkgo dry-extract medicines only after consulting a doctor [23]. NCCIH says ginkgo may increase the risk of bleeding in people taking anticoagulant drugs such as warfarin [18], and MSKCC notes adverse event reports of additive effects with NSAIDs [19]. LiverTox notes that several instances of excessive bleeding with ginkgo have been attributed to interactions with antiplatelet medicines or anticoagulants [25].

In an open-label randomized crossover study of 12 healthy men, 7 days of ginkgo before a single warfarin dose did not significantly change clotting status or warfarin levels [13]. It tested a single warfarin dose in healthy men, not long-term use [13].

For liver-enzyme interactions, a review of pharmacokinetic studies found that positive laboratory findings could not be replicated in humans, and that at up to 240 mg a day of the standardized extract EGb 761 no clinically relevant interaction was shown [14]. Doses above that led to weak induction of CYP2C19 (omeprazole) and weak inhibition of CYP3A4 (midazolam) activity [14]. The same review says interactions cannot be excluded for the poorly standardized extracts used in many food supplements [14].

MSKCC lists case reports suggesting ginkgo may reduce the effect of the HIV medicine efavirenz, and notes conflicting laboratory and case-report data on CYP1A2, CYP2D6 and CYP3A4 [19].

Health Canada also asks people taking diabetes, high blood pressure or seizure medicines to consult a practitioner before use [21]. MSKCC lists case reports of seizures in predisposed people or those on medicines that lower the seizure threshold [19].

These sources describe what has been reported, not what is right for any individual. See our guide to supplement interactions.

If you take any of these medicines, talk to your doctor or pharmacist before combining them with ginkgo.