Ginkgo Biloba: Memory, Circulation and Interactions — What the Evidence Says

Ginkgo biloba is often sold as the plant for memory and circulation. The reality is much narrower and more complex. For centuries, its leaves and seeds have been used in traditional Chinese medicine, but modern research focuses almost exclusively on highly processed leaf extracts manufactured according to a precise process. This is not a leaf picked from a tree, just any powder, or whatever capsule is sold online. The gap between marketing claims and scientific evidence is substantial. While touted for everything from brain enhancement in students to reversing age-related memory loss, the strongest research does not support such broad applications. For preventing dementia, the most robust trials show no benefit. In some people already diagnosed with mild to moderate dementia, a specific standardized extract has sometimes shown a modest improvement in cognition or daily-living scores, but the size and practical value of this effect remain debated among clinicians. > [!key] Key points > Ginkgo doesn't treat Alzheimer's disease and doesn't replace a diagnosis or proper care. It is not a cognitive enhancer for healthy individuals. The main safety concern is an increased risk of bleeding, especially when combined with anticoagulant and antiplatelet medications. Choosing a product requires careful attention to its preparation and standardization. ## Which preparation are we talking about? The ginkgo used in significant clinical studies is a concentrated dry leaf extract. Its final composition—and therefore its potential effects and risks—depends heavily on the manufacturing process: which parts of the leaf are used, the type of solvent (typically an acetone-water mixture), and subsequent purification and standardization steps. The most studied extract, known as EGb 761, is not interchangeable with a simple leaf powder, a homemade tea, or a non-standardized supplement. ### Understanding "Standardized Extract" When you see a product labeled as "standardized," it should specify the concentration of key active compounds. For ginkgo, high-quality extracts are typically standardized to contain: * **22-27% Ginkgo Flavone Glycosides:** These are powerful antioxidants that may help protect cells, including neurons, from oxidative damage. * **5-7% Terpene Lactones:** This group includes ginkgolides and bilobalide. They are believed to improve circulation by inhibiting a substance called platelet-activating factor (PAF), which is involved in blood clotting and inflammation. A product that only lists "Ginkgo biloba leaf, 500 mg" is likely just ground-up leaves. Its active compound levels are unknown and variable, and it won't produce the same results seen in trials using concentrated extracts. Furthermore, unpurified preparations can contain higher levels of ginkgolic acids, allergenic compounds that can cause severe skin reactions and digestive upset. Reputable manufacturers limit ginkgolic acids to a very low level, often less than 5 parts per million (ppm). ### Forms to Avoid: Raw Plant and Seeds Seeds and the raw plant are a different and more dangerous matter. The NCCIH, the U.S. federal agency for research on complementary and integrative health, explicitly notes that fresh (raw) ginkgo seeds are toxic when eaten and can cause serious adverse effects, including seizures. This is due to a compound called ginkgotoxin (4'-O-methylpyridoxine), which interferes with vitamin B6 activity in the body. While roasting can reduce the toxin's level, it does not eliminate the risk, and serious effects have been reported with roasted seeds or consuming the raw plant material. Using raw leaves to make tea is also not advised. The European Medicines Agency (EMA) has established monographs for certain well-defined leaf preparations for specific indications. That doesn't mean every food supplement on the market benefits from the same level of oversight, nor that their often-vague marketing claims are proven. When evaluating a product, the botanical name (*Ginkgo biloba*), the part used (leaf), the type and amount of extract, its standardization, and the listed warnings matter far more than the word "ginkgo." ## Memory: prevention, normal aging, and dementia The question "does ginkgo improve memory?" is too broad because it mixes together very different situations. A healthy student hoping to ace an exam isn't comparable to a person experiencing normal age-related forgetfulness, nor to someone who has been formally diagnosed with dementia. **Preventing dementia: a clear negative result.** The landmark Ginkgo Evaluation of Memory (GEM) trial provides the most definitive answer on prevention. This large, well-designed study enrolled 3,069 adults aged 75 and older, who had either normal cognition or mild cognitive impairment (MCI) at the start. Participants received either 120 mg of standardized EGb 761 extract twice a day or a placebo. After a median follow-up of 6.1 years, the results were unequivocal: ginkgo did not reduce the overall incidence of dementia, nor did it specifically prevent the development of Alzheimer's disease. This finding has led major health organizations to recommend against using ginkgo for dementia prevention. **Established dementia: a more nuanced and modest picture.** For individuals already diagnosed with dementia, the situation is slightly different. The Cochrane review published in 2026, a high-quality analysis of existing research, pooled 82 studies involving 10,613 participants. The studies used highly varied products and protocols, making firm conclusions difficult. However, within this dataset, 13 trials (3,288 participants) suggested a modest benefit from ginkgo at six months on measures of cognition and activities of daily living, with no notable difference in side effects compared with placebo. The authors stress that the benefit was small and its clinical relevance is debatable. Conclusions were less favorable for mild cognitive impairment, and longer-term effects remain uncertain. A 2025 meta-analysis focusing specifically on the EGb 761 extract found a favorable effect at a dose of 240 mg per day in 4 trials with 782 people diagnosed with mild dementia. This result is specific to *that extract* at *that dose* in *that population*. It cannot be extrapolated to other products, different doses, or self-treatment without a diagnosis. > [!evidence-conflicting] Evidence level: conflicting results > On the symptoms of dementia, results diverge depending on the extract, dose, and population studied. Some high-quality trials of standardized extracts find a modest, temporary benefit on symptoms, while others find no clinically meaningful improvement. There is no evidence that ginkgo prevents dementia or reverses neuronal damage. It should never replace a prescribed treatment or a comprehensive care plan managed by a physician. Some cognitive issues can stem from nutritional deficiencies, a factor that should be evaluated first, for example by checking [vitamin B12 levels](/en/article/vitamine-b12-alimentation-analyses-supplementation-risques). **Cognitive enhancement in healthy adults:** Many people, especially students and working professionals, are drawn to ginkgo as a "nootropic" or smart drug. However, the evidence for this use is extremely weak. Studies in healthy, younger individuals are often small, short-term, and produce inconsistent results. A systematic review of the evidence concluded that there is no convincing data to support the claim that ginkgo enhances memory, attention, or executive function in healthy people of any age. Those looking for cognitive support may find more consistent, though different, effects from other strategies, such as managing [caffeine intake](/en/article/cafeine-performance-sportive-dose-timing-tolerance-risques). ## "Circulation": what can and can't be said The word circulation is a vague umbrella term covering very diverse realities: heavy legs due to venous issues, leg pain from arterial disease, dizziness, tinnitus, or a simple feeling of cold hands and feet. A plausible mechanism observed in a laboratory, such as an effect on blood vessel tone or a reduction in oxidative stress, is not enough to demonstrate a clinical benefit in patients. According to the NCCIH, the available data do not support using ginkgo to prevent heart disease, stroke, or to treat high blood pressure. It is not a substitute for evidence-based interventions like appropriate physical activity, quitting smoking, blood pressure control, or prescribed medications. For specific circulation-related symptoms, the results are highly variable: * **Intermittent Claudication:** This condition involves cramping pain in the legs during exercise, caused by poor arterial blood flow. Early studies suggested ginkgo might improve pain-free walking distance. However, a major Cochrane review analyzing the data from multiple trials concluded that ginkgo was no more effective than a placebo. It is not recommended for this condition. * **Tinnitus (Ringing in the Ears):** The idea that ginkgo could help tinnitus by improving microcirculation to the inner ear is plausible, but clinical evidence is poor and contradictory. Some studies showed a small benefit, particularly for those with recent-onset tinnitus, while many others found no difference compared to placebo. It is not considered a reliable treatment. * **Dizziness and Vertigo:** Some older European studies found that the EGb 761 extract was as effective as a standard medication (betahistine) for certain types of vestibular vertigo. However, this evidence is not widely accepted everywhere, and it's crucial to first obtain a medical diagnosis to determine the cause of the dizziness. * **Raynaud's Phenomenon:** In this condition, blood vessels in the fingers and toes constrict dramatically in response to cold. A few small, preliminary studies suggested that ginkgo might reduce the frequency of attacks, but the evidence is considered insufficient to make a recommendation. > [!evidence-insufficient] Evidence level: insufficient for a general claim > The phrase "stimulates circulation" is too vague and misleading to accurately sum up the data. Results are highly dependent on the specific symptom, the underlying diagnosis, the preparation used, and the study's quality. No major clinical guideline supports presenting ginkgo as a first-line vascular treatment. For venous issues like heavy legs, other plants such as [horse chestnut](/en/article/marronnier-inde-jambes-lourdes-formes-preuves-precautions) may have more specific evidence. Sudden symptoms like new tinnitus, sudden hearing loss, weakness on one side of the body, or a sudden speech disturbance require prompt medical attention. A supplement should never delay this critical evaluation. ## Interactions and bleeding risk This is the most critical safety concern with Ginkgo biloba. Its ability to inhibit platelet-activating factor and potentially affect blood clotting mechanisms means it can increase the risk of bleeding, especially when combined with certain medications. The data are not entirely uniform: some small pharmacological studies found no measurable interaction with the anticoagulant warfarin, while a large observational study in U.S. veterans linked taking ginkgo together with warfarin to a significantly higher risk of a bleeding event (a hazard ratio of 1.38). This divergence is a strong reason to seek professional advice, not to test the combination yourself. Key interactions to be aware of include: * **Anticoagulants and Antiplatelet Drugs:** This is the most well-documented risk. Combining ginkgo with medications like warfarin, apixaban, rivaroxaban, dabigatran, aspirin, clopidogrel, or ticagrelor can substantially increase the risk of bruising and serious bleeding. * **Nonsteroidal Anti-inflammatory Drugs (NSAIDs):** Regular use of over-the-counter drugs like ibuprofen and naproxen also carries a bleeding risk, particularly in the gastrointestinal tract. Adding ginkgo can amplify this effect. * **Anticonvulsants:** This interaction is twofold. First, improperly prepared ginkgo products containing ginkgotoxin can lower the seizure threshold and may provoke seizures in people with epilepsy. Second, ginkgo may alter the metabolism of anticonvulsant drugs like carbamazepine and valproic acid, potentially reducing their effectiveness and leading to a loss of seizure control. * **Antidepressants:** There are case reports of increased bleeding risk when ginkgo is combined with SSRIs (e.g., fluoxetine, sertraline). Additionally, caution is advised with MAOIs due to theoretical risks. This highlights the importance of discussing all supplements, as other botanicals like [St. John's wort](https://www.nutri-facts.org/en/article/millepertuis-interactions-efficacite-precautions) also have major interactions with these drugs. * **Diabetes Medications:** Ginkgo may influence blood sugar levels and insulin metabolism. While studies are inconsistent, people taking insulin or other medications to lower blood sugar should monitor their levels closely if they start taking ginkgo, as adjustments may be necessary. * **Drugs Metabolized by Cytochrome P450 Enzymes:** Ginkgo can affect the activity of liver enzymes (such as CYP3A4, CYP2C9, and CYP2C19) that are responsible for breaking down a vast number of medications. This can either cause a drug to be cleared too quickly (reducing its efficacy) or too slowly (increasing its level and risk of toxicity). This applies to many common drugs, from statins to blood pressure medications. This metabolic complexity is another reason why a full medication review with a pharmacist is essential, similar to precautions needed with supplements like [curcumin](https://www.nutri-facts.org/en/article/curcuma-efficacite-formes-interactions). > [!caution] Caution before any use > Always seek medical or pharmacist advice before starting ginkgo if you take an anticoagulant, an antiplatelet medication, an anti-inflammatory, an anticonvulsant, an antidepressant, or any treatment with a narrow therapeutic margin. Discontinue ginkgo at least one to two weeks before any planned surgery or dental procedure. See a doctor promptly in the case of black or tarry stools, vomiting blood, unusual or easy bleeding, numerous unexplained bruises, sudden weakness, or a severe, unusual headache. ## Pregnancy, breastfeeding, and side effects For lack of sufficient safety data, ginkgo is not advised during pregnancy and breastfeeding. The NCCIH states it could be dangerous during pregnancy, citing a potential risk of inducing premature labor or causing increased bleeding during delivery. Data on its passage into breast milk and its effects on a nursing infant are limited, making avoidance the safest course. In non-pregnant adults, standardized leaf extracts have generally been well tolerated in studies, including over several years. This does not mean they are "risk-free." The most common side effects are generally mild and include: * Headaches * Dizziness * Digestive upset (nausea, gas, diarrhea, or constipation) * Heart palpitations * Allergic skin reactions (a rash or dermatitis) A hypersensitivity reaction is always possible. Children, individuals with a known clotting disorder or a history of seizures, and those taking multiple medications should avoid ginkgo unless specifically advised by a knowledgeable healthcare provider. A supplement should never be used to explain away, or to mask, progressive memory loss, which requires a proper medical workup. ## A Practical Checklist Before Buying Ginkgo Instead of impulsively buying a bottle based on a marketing claim, a thoughtful approach is necessary to ensure safety and avoid wasting money. 1. **Define the specific problem.** "I feel forgetful" is a vague starting point. Is this a new symptom? Is it getting worse? Are there other symptoms like dizziness or mood changes? A memory complaint, painful legs, or tinnitus deserves to have its cause investigated by a doctor first. 2. **Check your medications and health conditions.** Make a complete list of everything you take, including prescription drugs, over-the-counter pain relievers like aspirin and ibuprofen, and other herbal products or supplements like [omega-3s](https://www.nutri-facts.org/en/article/omega3-complements-epa-dha-choisir-securite). Review this list with your doctor or pharmacist specifically asking about ginkgo interactions. 3. **Learn to read the label.** A quality product will provide detailed information. Look for: * **Plant part:** *Ginkgo biloba* **leaf extract** (not just "leaf powder"). * **Extract ratio:** A higher ratio (e.g., 50:1) indicates a more concentrated product. * **Standardization:** It should state the percentage of flavone glycosides (22-27%) and terpene lactones (5-7%). * **Purity:** Look for a statement about low ginkgolic acid content (<5 ppm). * **Third-party certification:** Seals from organizations like USP, NSF, or ConsumerLab.com provide independent verification of the product's contents and purity. 4. **Account for timing.** Are you planning surgery or a dental procedure? Are you pregnant or breastfeeding? Have you recently started a new medication? Any of these situations significantly increases the level of caution needed. 5. **Set a measurable goal and a trial period.** If a professional approves a trial, define the specific symptom you want to track. For example, the frequency of Raynaud's attacks or scores on a standardized cognitive test (if monitored by a professional). Reassess after a defined period (e.g., 3-6 months). If there is no clear benefit, it is better to stop taking it than to continue indefinitely out of habit. No universal "ginkgo" dose can be inferred from the literature. The figures circulating online (e.g., 120-240 mg per day) most often correspond to a specific standardized extract (like EGb 761) for a specific indication. They do not carry over to another product without professional validation. ## FAQ ### Can ginkgo prevent Alzheimer's disease? No. The large, high-quality GEM trial, conducted in more than 3,000 older adults over about six years, showed that a standardized ginkgo extract did not reduce the risk of developing dementia or Alzheimer's disease compared to a placebo. ### Can ginkgo be combined with an anticoagulant like warfarin or aspirin? Not without explicit medical advice and monitoring. The bleeding risk is plausible and documented enough in some studies to make this combination potentially dangerous. A healthcare professional must weigh the risks and benefits for your specific situation. ### Does ginkgo improve memory in healthy young people? The evidence is weak, inconsistent, and of poor quality. Most studies show no significant benefit for memory, focus, or other cognitive functions in healthy adults. It is not a proven "study aid." ### Which form should be chosen? No form is universally equivalent. The most precise and reliable results come from studies using specific, standardized extracts (like EGb 761), which are purified to concentrate active compounds and remove harmful ones. A simple powder, tea, or tincture is not comparable. A professional can help check whether the product being considered matches the available data. ### Is ginkgo tea safe? Commercially prepared ginkgo teas from reputable brands are generally considered safe for consumption, as they are processed to reduce harmful components. However, they are not concentrated extracts and are unlikely to have the therapeutic effects seen in clinical trials. Tea made from raw, unprocessed leaves is not recommended. ### Why are ginkgo seeds toxic? Fresh and improperly cooked ginkgo seeds contain a substance called ginkgotoxin. This toxin interferes with the body's use of vitamin B6, a crucial nutrient for neurotransmitter function. This interference can lead to neurological symptoms, most seriously seizures. ## Sources - NCCIH, Ginkgo: Usefulness and Safety (2024): https://www.nccih.nih.gov/health/ginkgo/index.html - EMA, Assessment report on *Ginkgo biloba* L., folium (2014): https://www.ema.europa.eu/en/documents/herbal-report/final-assessment-report-ginkgo-biloba-l-folium_en.pdf - Wieland L.S. et al., Cochrane review, Ginkgo biloba for cognitive impairment and dementia (2026), PMID 41641880: https://pubmed.ncbi.nlm.nih.gov/41641880/ - DeKosky S.T. et al., GEM trial, JAMA (2008), PMID 19017911: https://pubmed.ncbi.nlm.nih.gov/19017911/ - Stoddard G.J. et al., ginkgo-warfarin interaction in U.S. veterans (2015), PMID 26958257: https://pubmed.ncbi.nlm.nih.gov/26958257/ - Riepe M. et al., EGb 761 meta-analysis in mild dementia (2025), PMID 39895346: https://pubmed.ncbi.nlm.nih.gov/39895346/ - Anses, herbal food supplements (2020): https://www.anses.fr/fr/content/complements-alimentaires-base-de-plantes-vers-une-meilleure-information-des-consommateurs > **Health information:** this article does not replace a diagnosis or a consultation. Seek advice from a doctor or pharmacist before any supplement if you are pregnant or breastfeeding, are on a treatment, have a clotting disorder or epilepsy, or have a new neurological or vascular symptom.