Overview

Ginkgo biloba is one of the most commonly used herbal supplements throughout the world. Ginkgo trees are among the oldest plant species in the world, according to the National Center for Complementary and Alternative Medicine. Medicinal use of the plant dates back centuries. Extensive research and studies have demonstrated its effectiveness in treating conditions such as dementia and poor circulation. Memory enhancement can also result from use of the supplement.

How Ginkgo Works

Ginkgo biloba's mechanism of action allows it to improve blood circulation in the body, which in turn allows the eyes, ears, brain and legs to work better, according to RXList. The seeds of the ginkgo biloba plant have properties that make them effective in killing infection-causing bacteria and fungi. Furthermore, it can slow the progress of Alzheimer's disease by altering brain changes that interfere with thinking ability.

Available Forms and Dosage

Ginkgo biloba supplements come in many forms, including capsules, tablets, extracts, tinctures and dried plant leaves that can be steeped to make a tea. Dosage depends on the condition being treated. People using the supplement to improve memory and heart function should take 120 milligrams a day in divided doses, according to the University of Maryland Medical Center. For patients with dementia or Alzheimer's disease, up to 240 mg daily in two or three doses is safe.

Side Effects

Ginkgo biloba is generally considered safe, but side effects may develop in some people. The most commonly reported side effects include upset stomach, nausea, diarrhea, headaches and dizziness, according to the National Center for Complementary and Alternative Medicine. Some people have also developed allergic reactions such as a rash, but more severe allergic reactions have also been reported.

Warnings

Some research suggests ginkgo can increase the likelihood of suffering severe bleeding, so people with bleeding disorders should speak with their doctor before using the supplement. In addition, because of this risk, users should stop taking it at least 36 hours before undergoing surgical procedures or major dental work, according to the UMMC. Furthermore, uncooked seeds from the plant contain a seizure-causing compound called ginkgotoxin. Because of this, people with epilepsy and other seizure-causing disorders are advised not to use ginkgo.

Drug Interactions

Ginkgo biloba supplements can interfere with the effectiveness of certain prescription drugs. For example, anti-seizure medications such as carbamazepine may be less effective, and use of ginkgo with antidepressants classified as selective serotonin re-uptake inhibitors increases the likelihood of a potentially fatal condition called serotonin syndrome, according to UMMC. The supplement can also interfere with insulin levels and may cause blood pressure to drop dangerously low in people taking medications to help lower blood pressure. Other drugs that may be affected by ginkgo include blood thinners, cyclosporine, thiazide diuretics and trazadone.