Saw palmetto side effects

Saw palmetto is generally well tolerated in the human trials that have tested it, including at doses up to three times the standard amount. The most common side effects are mild — stomach-related upset, headache, fatigue and decreased libido — while a single case report describes a more serious bleeding event worth knowing about.

What the research found

A 2009 systematic review searched five databases, WHO and national safety-reporting bodies, and contacted 24 manufacturers and distributors, finding 40 articles that reported on saw palmetto's safety in humans. It concluded that adverse events are mild and occur at a rate similar to placebo. The most frequently reported were abdominal pain, diarrhea, nausea, fatigue, headache, decreased libido and rhinitis. More serious events — including isolated reports of death and cerebral hemorrhage — turned up only in individual case reports and spontaneous safety-reporting data, and the review specifically notes that causality in those isolated reports is questionable. That review found no confirmed drug interactions in the literature it reviewed; see saw palmetto and medications: what to check for more on that, including a separate case involving bleeding.

That separate case, from 2001, describes one patient taking saw palmetto who experienced severe bleeding during surgery, with a prolonged bleeding time that returned to normal several days after stopping the herb. A single case report can't prove saw palmetto caused it, but the pattern — and the authors' review of the wider literature — is specific and serious enough that it's standard practice to tell a surgeon about any supplement, saw palmetto included, before a scheduled procedure. See who should not take saw palmetto for more on that.

Questions people ask

What are the side effects of saw palmetto?

The most commonly reported are mild: stomach-related upset (abdominal pain, diarrhea, nausea), fatigue, headache, decreased libido and rhinitis. A 2009 safety review found these occur at a rate similar to placebo across the trials it reviewed.

What are the long-term side effects of saw palmetto?

The longest controlled trials followed people for up to about a year and a half (72 weeks). Within that window, no unusual long-term safety signal emerged beyond the mild effects listed above, even at three times the standard dose. No trial has followed people for longer than that, so anything beyond roughly 18 months is outside what the research covers.

Does saw palmetto have side effects?

Yes, though they're generally mild in the research: gastrointestinal upset, headache, fatigue and decreased libido are the most commonly reported. Serious events are rare and, in the cases reported, of uncertain cause.

Does saw palmetto make you sleepy?

Fatigue is among the side effects reported in the safety review, but that's distinct from drowsiness or a sedative effect specifically, which hasn't been studied as its own outcome.

Can saw palmetto cause dizziness?

Dizziness doesn't appear among the most commonly reported side effects in the systematic review covering 40 studies. If it happens to you, stop taking it and talk to a doctor, since that review's data can't rule out an individual reaction.

When to talk to a doctor

Stop taking saw palmetto and tell a doctor about any unusual bleeding, bruising, or a change in libido that concerns you. Tell a surgeon or anesthesiologist that you take saw palmetto before any scheduled procedure, given the documented bleeding-related case above. Talk to a doctor before starting saw palmetto if you're pregnant, nursing, or take prescription medication, since the safety evidence in those situations is more limited than the general data above.

Related reading: who should not take saw palmetto, saw palmetto and medications: what to check, and how much saw palmetto should you take a day.