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St. John's Wort Dosage

Although the safest, most effective dose of St. John's wort has not been clearly established, clinical studies have provided some general dosing guidelines. Most studies on St. John's wort for depression used doses of 300 mg of an extract three times daily. However, because different products may contain a different St. John's wort dosage, it's best to follow the directions on each particular label.

 

St. John's Wort Dosage: An Introduction

It is important to note that unlike medications, for which standard doses have been well established, less information is available for determining the best dose of supplements, including St. John's wort (Hypericum perforatum). However, some information is available about St. John's wort dosing, based on a few clinical studies and practical experience with the supplement.
 

What Is a Reasonable St. John's Wort Dose?

Most studies of St. John's wort for treating depression used doses of 300 mg of a St. John's wort extract (standardized to 0.3 percent hypericin content) three times daily. "Standardization" means that the extracts were tested to make sure they had a standard amount of hypericin (one of the active chemical components of St. John's wort). Other studies suggest that a single daily dose, instead of three times a day, may also be effective.
 
Different products may contain different amounts of the active chemicals of St. John's wort, even if the "strengths" listed on the labels are the same. Therefore, it is best to follow the dosing instructions provided on the label of your particular product.
 

General Information on Dosing With St. John's Wort

Considerations for people taking St. John's wort include the following:
 
  • Because the manufacturing of supplements such St. John's wort is not closely regulated, it is important to choose a trustworthy manufacturer for your supplements. Your pharmacist can help you choose a reputable manufacturer.
     
  • Taking St. John's wort late in the day may increase the risk of insomnia.
     
  • If you have any chronic health problems or take any prescription medications, check with your healthcare provider before taking St. John's wort.
     
  • St. John's wort is likely to interact with many medications. Therefore, if you take any medications, check with your healthcare provider before taking St. John's wort (see St. John's Wort Drug Interactions).
     
  • If you are unsure about anything related to your dosage or St. John's wort dosing in general, please talk with your healthcare provider.
     
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Written by/reviewed by: Kristi Monson, PharmD; Arthur Schoenstadt, MD
Last reviewed by: Kristi Monson, PharmD;