Saw palmetto side effects
Executive summary
Saw palmetto is a widely used herbal supplement most commonly taken for benign prostatic hyperplasia (BPH) and sometimes for hair loss; short-term use appears generally safe with mostly mild gastrointestinal and neurologic complaints reported [1] [2]. Rare but more serious concerns — including bleeding risk when combined with anticoagulants, potential hormonal effects in women of childbearing age, and isolated case reports of liver injury — require caution and discussion with a clinician [3] [4] [5].
1. What saw palmetto is and why people take it
Derived from the berries of Serenoa repens, saw palmetto is marketed for urinary symptoms of an enlarged prostate and for androgen-related hair loss because it may inhibit 5-alpha-reductase and reduce dihydrotestosterone (DHT) formation, though clinical benefit for these uses is inconsistent in reviews [1] [6].
2. The common, mild side effects documented in trials
Randomized trials and reviews report that the most frequently observed adverse effects are gastrointestinal upset (nausea, abdominal pain, diarrhea, constipation), headache, fatigue, and decreased libido; these side effects are generally mild and occur at rates similar to placebo in several studies [4] [7] [8].
3. Rare but serious risks and drug interactions that merit attention
Though uncommon, case reports and spontaneous reports have linked saw palmetto to clinically apparent liver injury and, in isolated reports, severe bleeding or cerebral hemorrhage — causality is disputed but these events appear rare [4] [7]. Multiple sources also flag potential interactions with anticoagulants and antiplatelet drugs (warfarin, aspirin, clopidogrel) and with NSAIDs, and in vitro data suggest effects on drug‑metabolizing enzymes (CYP3A4, UGTs), meaning additive bleeding or altered drug levels are plausible and warrant caution [3] [8] [9].
4. Who should avoid saw palmetto or use extra caution
Women who are pregnant, trying to become pregnant, or breastfeeding should avoid saw palmetto because of its hormonal activity and theoretical risks to a male fetus; children are also advised not to take it [3] [5]. People taking anticoagulants, antiplatelet drugs, NSAIDs, or certain prescription medicines should consult a clinician before use because of possible additive bleeding or metabolic interactions [3] [8] [10].
5. What the evidence does — and doesn’t — say about safety
Large, well-conducted trials such as the STEP assessment found no clinically important adverse effects over one year at common doses, and many systematic reviews report side effects similar to placebo, supporting an overall favorable short‑term safety profile; however, variability in product formulations, limited data in women and pregnant people, and sporadic serious case reports create uncertainty about rare harms and long‑term risks [11] [6] [7].
6. Practical takeaway for clinicians and consumers
For most adult men considering saw palmetto for urinary symptoms, short-term use appears low-risk but likely provides little or no benefit for BPH symptoms according to recent reviews; anyone on blood thinners, antiplatelets, NSAIDs, hormonal therapies, or with liver disease should avoid or discuss it with their clinician, and pregnant or breastfeeding people should not use it due to theoretical fetal/reproductive risks [6] [3] [4]. When used, choose standardized products, report any unusual bleeding, jaundice, severe abdominal pain, or neurological symptoms promptly, and inform health providers about supplement use because herb–drug interactions and product variability are real concerns [8] [11].