Ginkgo Biloba Risks and Benefits

The Bottom Line

Ginkgo biloba is used by many people in an effort to improve memory and slow age-related intellectual decline, but solid evidence to support these benefits is limited. Ginkgo biloba is generally considered safe, but it can cause adverse effects and interactions with other drugs.

The Full Story

Everyone wants to maintain memory and brain sharpness as they age, so there is strong interest in Ginkgo biloba as a supplement to prevent mental decline associated with both normal aging and dementia.

Ginkgo biloba is an herbal supplement made from the leaves of the Ginkgo tree, also known as the maidenhair tree. Ginkgo trees are native to China but are now grown worldwide. Ginkgo biloba is categorized as "nootropic," meaning it's thought by some to be a cognitive enhancer (related to conscious intellectual activity such as thinking, memory, and reasoning). It is prescribed as a memory and concentration booster in many countries and is widely available as an over-the-counter herbal supplement in the US. Ginkgo is thought to increase blood supply by dilating blood vessels, reducing blood viscosity (thickness), affecting neurotransmitters, and reducing free radicals. For healthy adults, Ginkgo biloba appears to be safe when taken orally in moderate amounts.

But Is It Effective?

A randomized, double-blind, placebo-controlled clinical trial, The Ginkgo Evaluation of Memory (GEM) study, examined whether a twice daily 120 mg dose of Ginkgo biloba extract might help delay or prevent dementia in 3609 older adults aged 72 to 96 years. The study was conducted in six US academic medical centers between 2000 and 2008. Several assessment tools, such as the Modified Mini-Mental State Examination (MMSE) and the cognitive subscale of the Alzheimer Disease Assessment Scale, measured outcomes over time. The investigators concluded that compared with placebo, the dosage of Ginkgo biloba used didn't result in less cognitive decline in older adults with normal cognition or with mild cognitive impairment.

The subjects in this study were probably older than most people who start taking Ginkgo biloba to help prevent cognitive decline. There are no studies specifically evaluating people taking Ginkgo biloba to ward off intellectual decline and memory loss at younger ages.

A prospective, community-based, cohort study, PAQUID, gathered data from 3612 participants aged 65 and older without dementia and followed the participants for 20 years. Three groups were compared: 589 subjects reported use of EGb761 (a standardized extract of Ginkgo biloba leaves) during at least one of the assessment visits, 149 participants reported use of piracetam (a nootropic drug), and 2874 did not report use of either drug. Data analysis showed that the decline of the MMSE score in a population of non-demented subjects was less in the group who reported using EGb761 than in those who did not. This effect appeared to be a specific effect of EGb761 since it wasn't observed in the piracetam or other group.

These results seem to contradict the GEM study findings. However, data from the PAQUID study were collected from volunteer subjects motivated to enter a study on prevention of memory decline. It might be a "healthy participant" effect; the subjects might have practiced risk reduction behaviors and they selected their own treatment rather than having it assigned randomly by the investigators. Although the GEM study was a more rigorous design, the PAQUID study was of much longer duration. Cognitive decline is usually a slow process. A short study might be insufficient to correctly assess various impacts on cognitive decline.

Several randomized, double-blind studies compared use of Ginkgo biloba at any strength and over any period of time with a placebo, looking for effects on people with cognitive impairment including dementia. Most of these studies were small and of short duration, often less than 3 months. When the data from these studies were pooled, the results showed inconsistent evidence that Ginkgo biloba had any predictable and clinically important benefits for people with dementia or cognitive impairment.

Based on current evidence, taking Ginkgo biloba probably will not help prevent or slow the onset of dementia or intellectual decline. It might possibly be effective when started at younger ages such as in the 50s, but this has not been studied. Ginkgo biloba can interact with some medications and can cause side effects including bleeding.

If you think someone has taken too much Ginkgo biloba or is having a bad reaction, do not make the person vomit. Immediately check the webPOISONCONTROL® online tool for guidance or call Poison Control at 1-800-222-1222.

Mary Elizabeth May, RN, BA, MPH
Certified Specialist in Poison Information

For More Information

Ginkgo [internet]. Bethesda MD. National Center for Complementary and Integrative Health. Sep 2016 [accessed Feb 26, 2018].


Amieva H, Meillon C, Helmer C, Barberger-Gateau P, Dartigues JF. Ginkgo biloba extract and long-term cognitive decline: a 20-year follow-up population-based study. PLoS One 2013;8:e52755.

Birks J, Grimley Evans J. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database Syst Rev 2009:CD003120.

Diamond BJ, Bailey MR. Ginkgo biloba: indications, mechanisms, and safety. Psychiatr Clin North Am 2013;36:73-83.

Miwa H, Iijima M, Tanaka S,  Mizuno Y. Generalized convulsions after consuming a large amount of ginkgo nuts. Epilepsia 2001;42:280-1.

Pedroso JL, Henriques Aquino CC, Escorcio Bezerra ML, et al. Ginkgo biloba and cerebral bleeding: a case report and critical review. Neurologist 2011;17:89-90.

Snitz BE, O'Meara ES, Carlson MC, et al. Ginkgo biloba for preventing cognitive decline in older adults: a randomized trial. JAMA 2009;302:2663-70.

Vale S. Subarachnoid hemorrhage associated with Ginkgo biloba. Lancet 1998;352:36. 


Call 1-800-222-1222 or

HELP ME online

Prevention Tips

  • Ginkgo biloba can interact with some conventional medications such as anticoagulants (blood thinners). Tell all your healthcare providers about any complementary, herbal, or integrative health approaches you use.
  • The American Society of Anesthesiologists recommends that all herbal medications be discontinued 2 to 3 weeks prior to elective surgery. Ginkgo biloba is specifically mentioned due to its potential to increase bleeding.
  • Side effects of Ginkgo biloba include headache, stomach upset, and allergic skin reactions. If you're older, have a known bleeding risk, or are pregnant you should be aware that Ginkgo biloba might increase your risk of bleeding.
  • Do not eat fresh (raw) or roasted Ginkgo seeds. These can be poisonous and have serious side effects.

This Really Happened

Case 1. A previously healthy 38-year-old woman had sudden onset of left-sided weakness and slurred speech. She had been taking Ginkgo biloba 240 mg and thiamine 900 mg daily for 4 years as recommended by her physician for leg pain. A CT scan showed bleeding in her brain. Cerebral angiography and MRI ruled out any structural abnormalities that might explain her brain hemorrhage. Ginkgo biloba was considered a probable cause of her bleeding. Eventually, she partially recovered her strength.

Case 2. A 36-year-old woman without a personal or family history of epilepsy came to an emergency room with frequent vomiting and generalized seizures. About 4 hours before the onset of seizures she had consumed approximately 70-80 Ginkgo nuts, the seeds of Ginkgo biloba, since she had heard of possible health benefits. She was treated with anticonvulsant medications. Imaging of her brain and testing of her spinal fluid were normal. Epilepsy was ruled out, and her diagnosis was seizures most likely caused by consumption of Ginkgo nuts.

Case 3. A previously healthy 61-year-old man developed headache, back pain, nausea, and sleepiness while taking Ginkgo biloba 40 mg tablets 3-4 times a day for more than 6 months. Although his CT scan was normal, spinal fluid examination showed bleeding in his brain. The Ginkgo was stopped, and he had no further bleeding.