Ginkgo and warfarin: Risks, interactions, and what you need to know

When you take Ginkgo and warfarin, a herbal supplement and a prescription blood thinner that both affect how your blood clots. Also known as Ginkgo biloba and coumadin, this combination can lead to serious bleeding—sometimes without warning. Many people think herbal supplements are safe because they’re "natural," but that’s not true when they mix with medications like warfarin.

Warfarin is a blood thinner, a drug used to prevent dangerous clots in people with atrial fibrillation, artificial heart valves, or a history of stroke. It works by slowing down your body’s clotting process. Ginkgo biloba, a popular herb for memory and circulation, also interferes with clotting by affecting platelets and blood vessel tone. When you take them together, the effect multiplies. Studies show this mix can raise your risk of bruising, nosebleeds, internal bleeding, and even brain hemorrhages. One 2019 case report described a 72-year-old woman who developed a life-threatening brain bleed after taking Ginkgo for three weeks while on warfarin—she hadn’t told her doctor about the supplement.

This isn’t just about Ginkgo. Other herbal supplements, like garlic, ginger, ginseng, and fish oil can do the same thing. But Ginkgo is one of the most common culprits because people take it without realizing it’s risky. Many older adults use it for memory, thinking it’s harmless. But if you’re on warfarin, even a small daily dose of Ginkgo can throw off your INR levels—those numbers your doctor checks to make sure your blood isn’t too thin or too thick.

The real problem? Most patients don’t tell their doctors about supplements. They assume it’s not important, or they think the doctor won’t care. But your pharmacist or provider needs to know everything you’re taking—even if it’s from the health food store. A simple blood test can catch dangerous changes before they cause harm.

If you’re on warfarin and want to support brain health, there are safer options. Regular exercise, good sleep, and controlling blood pressure do more for memory than Ginkgo ever could. And if you’re already taking Ginkgo, don’t stop cold turkey—talk to your doctor first. They might adjust your warfarin dose or suggest a different supplement that won’t interfere.

Below are real-world stories and expert-backed guides on how medications and supplements interact—like how zinc affects antibiotics, how biotin messes with lab tests, and why some painkillers can damage your kidneys. These aren’t theoretical warnings. These are situations real people face every day. What you read here could keep you out of the ER.