Because St. John's wort (Hypericum perforatum) is a supplement rather than a medication, less information is available about the safest and most effective dosage. Based on clinical studies and practical experience with the supplement, a dosage of 300 mg of a St. John's wort extract taken three times daily was used for treating depression. However, because different products may contain different amounts of the supplement, you should follow the dosing directions on each particular product label.
(To learn more about St. John's wort dosing guidelines, click St. John's Wort Dosage. This article also offers tips on when and how to take this supplement.)