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Saw palmetto is an extract of the berries of a small palm native to the southeastern United States, and it is one of the most popular herbal supplements sold to men. The research has not been kind to it. Two large, government-funded trials found it worked no better than a placebo for urinary symptoms linked to an enlarged prostate, and a 2023 Cochrane review of 27 trials reached the same conclusion. Evidence for hair loss comes from a handful of small studies. Side effects are usually mild, but there are case reports of bleeding, and it is not for pregnancy. Here is what the studies actually show.
Peptide Labs sells dietary supplements, but none of our products contain saw palmetto, and this article does not recommend any product. It is general information, not medical advice.
Key Takeaways
- Saw palmetto comes from the berries of Serenoa repens, a palm native to the West Indies and southeastern US.
- The STEP and CAMUS trials found no difference from placebo for prostate-related urinary symptoms.
- A 2023 Cochrane review of 27 trials found little to no benefit when saw palmetto is used alone.
- Hair loss studies are small, often open-label and often test multi-ingredient products.
- Side effects are usually mild, but bleeding case reports mean blood thinners and surgery need a clinician's input.
What is saw palmetto?
Saw palmetto (Serenoa repens, also listed as Sabal serrulata) is a small tree that grows 6 to 10 feet tall along the southeast coast of North America and in the West Indies, according to the National Center for Complementary and Integrative Health (NCCIH). Supplements use extracts of its dark berries, usually as softgels or capsules, and often in “men’s health” or hair formulas that combine it with zinc, pumpkin seed, beta-sitosterol or biotin.
Interest in the herb comes from lab research suggesting it may act on 5-alpha-reductase, the enzyme that turns testosterone into dihydrotestosterone (DHT). DHT plays a role in both prostate growth and male-pattern hair loss, which is why the same herb is marketed for both. A plausible mechanism in a dish, however, does not always lead to a measurable effect in people, and that gap is the main story of saw palmetto research.
Saw palmetto benefits: what the prostate research found
Most saw palmetto research looked at benign prostatic hyperplasia (BPH), a noncancerous enlargement of the prostate that becomes common with age and can cause frequent urination, a weak stream and waking at night to urinate. Early, smaller studies looked encouraging. The larger and better designed trials that followed did not.
| Study | Who took part | Length | Main result |
|---|---|---|---|
| STEP, NEJM 2006 | 225 men over 49 with moderate-to-severe symptoms | 1 year | No difference from placebo in symptoms, urine flow, prostate size or PSA |
| CAMUS, JAMA 2011 | 369 men aged 45 and older at 11 sites | 72 weeks | No better than placebo, even when the amount was raised to three times the standard |
| Cochrane review, 2023 | 27 trials, 4,656 men | Up to 17 months | Little to no difference in symptoms or quality of life when used alone |
In the CAMUS trial, which was funded by the National Institutes of Health, symptom scores improved in both groups over 72 weeks, but slightly more in the placebo group. That pattern is a reminder that urinary symptoms often ease on their own or with expectation, which is why placebo-controlled trials matter. The Cochrane authors rated the evidence for saw palmetto alone as high certainty and noted that ten of the included studies were funded by industry. They were less certain about combination products, where saw palmetto is one of several plant extracts.
Two practical points follow from this research. First, urinary symptoms have several possible causes, so they deserve a proper evaluation by a clinician rather than a guess at the supplement aisle. Second, NCCIH notes that saw palmetto does not appear to change PSA readings, so taking it should not distort that blood test, but you should still tell whoever orders it what supplements you use.
Saw palmetto for hair loss
Saw palmetto for hair loss is a newer marketing angle, built on the same DHT idea. The evidence is thin. A 2020 systematic review in Skin Appendage Disorders found only five randomized trials and two cohort studies, using oral or topical products that often mixed saw palmetto with other ingredients. The results it reported were positive, but the authors stated that robust, high-quality data are lacking and that large trials of saw palmetto alone are needed.
- A 2002 placebo-controlled pilot study rated 6 of 10 men on a saw palmetto and beta-sitosterol formula as improved; the trial was too small to draw firm conclusions.
- A two-year open-label study of 100 men found that 38% improved with saw palmetto compared with 68% with finasteride, a prescription medicine; there was no placebo group and participants knew what they took.
- NCCIH sums up the hair research as too limited to allow conclusions.
Hair shedding also has many causes that a supplement will not address, including thyroid problems, low iron, stress and rapid weight loss. If you have noticed shedding after starting a weight-loss medicine, our article on GLP-1 hair loss explains what is known. Zinc is a common partner ingredient in hair formulas; our zinc guide covers why more is not better. A dermatologist can sort out which type of hair loss you have and which proven options fit.
Saw palmetto side effects and safety
Saw palmetto side effects are usually mild. NCCIH describes it as well tolerated in studies lasting up to three years, with infrequent digestive symptoms, dizziness and headache. Memorial Sloan Kettering Cancer Center (MSKCC) also lists diarrhea, tiredness, decreased libido and a runny nose, mostly at rates similar to placebo. The more serious concerns are less common:
- Bleeding. MSKCC cites case reports of severe bleeding during surgery and of impaired clotting. It advises against combining saw palmetto with warfarin or other blood thinners, antiplatelet drugs such as clopidogrel, or NSAID pain relievers. Tell your surgeon and dentist about it well before any procedure.
- Hormonal effects. Because it may act on sex hormone pathways, saw palmetto is not suited to children; MSKCC describes a girl who developed hot flashes after taking it. Anyone using hormonal birth control or hormone therapy should check with a clinician first.
- Pregnancy and breastfeeding. NCCIH says it may be unsafe during pregnancy or while breastfeeding.
- Medicine interactions. Lab research suggests it may affect liver enzymes that process many drugs, so a pharmacist should review it against your medicine list.
Checking a saw palmetto label
Products differ in the type of extract, the solvent used and the other herbs in the blend, and research on one extract may not apply to another. Look for the botanical name, the plant part (berry or fruit), and an independent testing seal. Our guide to third-party tested supplements explains what those seals do and do not confirm. If you are comparing herbs sold for hormones or blood sugar, our fenugreek guide looks at another popular seed extract with a similar gap between marketing and evidence.
Frequently Asked Questions
What is saw palmetto used for?
It is mostly marketed for prostate-related urinary symptoms and for male-pattern hair loss. Large trials did not find it better than placebo for urinary symptoms, and hair evidence is limited.
Does saw palmetto lower DHT?
Lab studies suggest it may act on the enzyme that makes DHT, but no strong human trials show a meaningful effect, and the prostate trials found no clinical benefit.
What are the common saw palmetto side effects?
Mild stomach upset, diarrhea, headache, dizziness and tiredness. Bleeding problems have been reported in case reports, so tell your clinician before surgery or if you take blood thinners.
Can women take saw palmetto?
It may be unsafe during pregnancy or breastfeeding, and it may affect hormones. Women considering it for hair thinning should see a dermatologist first.
Does saw palmetto affect PSA tests?
NCCIH says it does not appear to affect PSA readings, even in higher-than-usual amounts. Still tell your clinician you take it.
Is saw palmetto approved for prostate problems?
No. It is sold as a dietary supplement, which does not require proof of effectiveness. Urinary symptoms should be checked by a clinician.
Questions about a label? Contact us or read our Buyer’s Guide. Follow the label and ask a healthcare provider before starting any supplement, especially if you take medicines. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Last reviewed October 2026.
Related guides: Hair Growth Vitamins: Do Hair Vitamins Work, and Who Needs Them?, GLP-1 Hair Loss: How Common It Is and What Causes It, Biotin Side Effects, Benefits and the Lab Test Problem.