Summary
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What is ginkgo?
Ginkgo supplements contain leaf extracts of the Ginkgo biloba tree, but there is concern over the quality of extracts due to reported adulteration. (See What It Is). -
Do ginkgo supplements work?
Preliminary evidence suggests that ginkgo may modestly improve limited aspects of memory and cognition in healthy individuals, but stronger evidence indicates no significant benefit from ginkgo in preventing or treating Alzheimer's disease or other dementias. Preliminary evidence suggests ginkgo may be helpful in other conditions such as vertigo, intermittent claudication and Raynaud's disease. (See What It Does). -
What did CL's tests of ginkgo find?
Only 4 of the 10 popular ginkgo supplements ConsumerLab.com selected for testing were "Approved" in testing. An additional three products tested through CL's voluntary Quality Certification Program were also "Approved." -
Problems with ginkgo:
One product was discovered to contain no more than 3% of its listed amount of ginkgo extract. Several others appear to be have been adulterated ("spiked") with compounds from plants other than ginkgo — a common trick to make low-quality ginkgo appear to be higher in quality. (See What CL Found and use the Results table). 
Best Ginkgo biloba supplement?
Among the "Approved" products, ConsumerLab chose its Top Pick based on quality, dosage, and value: The product costs only 9 cents per 120 mg dose, while other "Approved" products cost two to thirty times as much for the same amount of ginkgo extract.-
What to look for in ginkgo supplements?
Ginkgo biloba (leaf) extracts used in clinical trials are typically standardized to contain 24% flavonol glycosides and 6% terpene lactones -- look for this on labels (but don't trust it unless it's been tested by a reputable 3rd party). (See ConsumerTips™). -
Safety and side effects of ginkgo:
Ginkgo is generally safe but can cause mild side effects. However, people with bleeding disorders, on blood-thinners or diabetes medication, and those trying to conceive should not take ginkgo. For details, see Concerns and Cautions.
