Merck Manual

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Saw Palmetto


Laura Shane-McWhorter

, PharmD, University of Utah College of Pharmacy

Last full review/revision Jul 2020| Content last modified Jul 2020
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NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
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Saw palmetto berries contain the plant’s active ingredients, which are fatty acids. The plant’s berries can be made into tea. Saw palmetto is also available as tablets, capsules, and a liquid extract. (See also Overview of Dietary Supplements.)

Medicinal claims

Saw palmetto opposes the actions of testosterone. Many men take saw palmetto to treat benign enlargement of the prostate gland (benign prostatic hyperplasia). In a number of studies, saw palmetto relieved the symptoms of an enlarged prostate gland, such as frequent urination. Although well-designed studies did not show any benefit from saw palmetto for those symptoms, some evidence suggests that a specific chemical extracted from saw palmetto decreases night-time urination and improves urine flow.

Claims that it increases sperm production, breast size, or sexual vigor are unproved.

Possible side effects

Headache and diarrhea occasionally occur. Because saw palmetto may have hormonal effects, women who are pregnant or who may become pregnant should not take it. There has been a case reported of acute liver damage and a case of pancreatitis possibly due to saw palmetto.

Possible drug interactions

Women taking hormone therapy should consult their doctor before they take saw palmetto. Saw palmetto may interact with estrogen therapy and oral contraceptives and may decrease warfarin's blood clot–preventing effects.

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

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