No side effects following proper administration of designated therapeutic dosages. In pooled clinical trials involving 10,000 patients, the incidence of side effects produced by Ginkgo Biloba extract was extremely small. There were few cases of headaches, dizziness, palpitation, gastrointestinal disturbances, bleeding disorders & skin hypersensitivity reactions. In higher than recommended doses, diarrhea, nausea, vomiting, restlessness, and weakness may occur.