Milk Thistle Dosage
Because dietary supplements do not require FDA approval, there is little information available about the safest and most effective dose of milk thistle supplements. Some studies have used dosages of 420 mg daily to 600 mg daily (divided into three smaller doses). However, it's a good idea to follow the milk thistle dosage instructions provided on the label of your particular product, because various supplements can contain a different amount of the active ingredient.
As with most herbal supplements, the most effective and safest doses for milk thistle have not been scientifically established yet. However, basic dosing guidelines can be obtained from clinical studies of milk thistle.
With prescription (and non-prescription) medications, researchers establish the most effective and safest doses in special studies, known as dose-range studies. These studies are done early in the development of medications, long before they are ever approved. However, because dietary supplements do not require FDA approval, dose-range studies are rarely performed. Without such studies, only vague "trial and error" information is typically available. Even if some clinical studies were available (as is the case with milk thistle), usually only one dose is studied, and it is impossible to know if a different dose would be safer or more effective.
Most studies that used milk thistle for treating liver disease used a 420 mg daily dose of a specific milk thistle product that contained 70 to 80 percent silymarin, the active component of milk thistle. One study of milk thistle for diabetes used a silymarin milk thistle extract, with a dose of 200 mg three times daily.
Because various milk thistle supplements may contain different amounts of silymarin, it is reasonable to follow the dosing instructions provided on the label of your particular product.