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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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Saw palmetto (Serenoa repens, Serenoa serrulata) berries contain the plant’s active ingredients. The active ingredients, thought to be fatty acids, seem to inhibit 5-alpha-reductase, thus opposing the conversion of testosterone to dihydrotestosterone. The berries can be used to make a tea, or they can be extracted into tablets, capsules, or a liquid preparation. Most formulations evaluated in clinical studies are hexane extracts of saw palmetto berries, which are 80 to 90% essential fatty acids and phytosterols.


Many men report use of saw palmetto to treat symptoms (eg, frequent urination) of benign prostatic hyperplasia (BPH). Additional claims are that saw palmetto increases sperm production, breast size, and sexual vigor. Dose is 320 mg once/day or 160 mg twice a day.


There is no scientific evidence to suggest that saw palmetto reverses BPH. A double-blind, multicenter, placebo-controlled randomized trial of 369 men found that increasing doses of a saw palmetto fruit extract did not reduce lower urinary tract symptoms more than placebo (1). In addition, a 2012 Cochrane review of 32 randomized, controlled trials, determined that saw palmetto, at double and triple doses, did not improve urinary flow measures or prostate size in men with lower urinary tract symptoms consistent with BPH (2). However, a 2018 systematic review and meta-analysis of 27 studies (5800 subjects) of a specific hexanic extract of saw palmetto found decreased nocturia and improved urine flow (3). A small, randomized, controlled trial reported that saw palmetto used for 2 months prior to transurethral resection of the prostate resulted in shortened surgery duration and a more favorable postoperative course (4). Claims that saw palmetto increases sperm production, breast size, or sexual vigor are unsupported.

Adverse effects

Headache and diarrhea may occur, but few serious adverse effects have been reported. One case report of a 58-year-old white man taking 900 mg of dried extract and 660 mg of berry powder to ease the symptoms of BPH reported acute liver damage due to saw palmetto (5). Another report of a 65-year-old male indicated that supplementation with saw palmetto may have been responsible for acute pancreatitis (6).

Saw palmetto may interact with estrogens; thus, women who are pregnant or who may become pregnant should not take it.

Drug interactions

No interactions have been reported for saw palmetto (7); however, although strong evidence is not available, patients on warfarin should be careful when considering or taking saw palmetto because of a possible risk of hepatotoxicity or bleeding.

Saw palmetto references

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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NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
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