The Risky Side Effects of Supplements

Medically Reviewed

Supplements can have powerful and sometimes unforeseen effects on the body. They can affect:

Bleeding and coagulation. Many herbs interfere with blood clotting—a dangerous effect if you’re taking an anticoagulant, have a bleeding disorder or are scheduled for surgery.

Blood sugar. Herbs can lower or raise your blood sugar, even if you don’t have diabetes.

Liver enzymes. Herbs can affect the production of liver enzymes, interfering with the liver’s ability to process medication. Subsequent interactions or adverse effects can range from ineffectiveness to toxicity.

Blood pressure. A number of herbal supplements can make your blood pressure dangerously high or low.

Hormones. Some herbal supplements have hormone-like actions and affect hormone levels. Hormone-sensitive conditions like breast, uterine or ovarian cancers can be made worse by exposure to supplements that act like estrogen or other hormones.

The following five drugs have the greatest number of reported interactions with herbal and dietary supplements:

Warfarin (Coumadin)




Ticlopidine (Ticlid)