Limited evidenceMen's health

DHT Blocker Formulas

Saw palmetto-based blends sold to block dihydrotestosterone and slow hair loss. Saw palmetto does inhibit 5-alpha-reductase in the test tube, but the human hair trials are small, short and often run by the manufacturer, and the effect is far below finasteride.

Evidence last reviewed: August 2026

What the science says

Saw palmetto for androgenetic alopecia Limited evidence
A 2025 systematic review and network meta-analysis of 19 randomized trials (1,658 patients, 16 different supplements) found saw palmetto extract improved blinded investigator assessment of hair regrowth, but it was not among the supplements that significantly improved hair density. The included trials were small and heterogeneous.
Individual trials are short and industry-run Limited evidence
A 90-day randomized trial of a proprietary saw palmetto fatty-acid extract in adults with self-perceived thinning hair reported improved hair counts, but was single-centre, short and sponsored. No trial has compared a DHT blocker blend with finasteride head to head.
Sexual and mood side effects are reported Limited evidence
A 2026 case series described sexual and psychiatric adverse effects following Serenoa repens use, proposing a 'post-Serenoa syndrome' analogous to reports around finasteride. Case series cannot establish causation, but the assumption that saw palmetto is automatically side-effect-free is not safe.

Dosage & safety

Studied doseTrials use 320 mg per day of a liposterolic saw palmetto extract standardized to about 85–95% fatty acids, taken for at least 3–6 months before judging any effect. Doses of the other ingredients typically bundled in (biotin, pumpkin seed oil, nettle root, zinc) are not individually validated for hair loss.

SafetyGenerally mild gastrointestinal upset and headache. Reported sexual dysfunction and mood changes in a minority of users. Saw palmetto has weak antiplatelet activity, so use caution with anticoagulants and before surgery. It can lower PSA readings and mask prostate cancer screening. Women who are or may become pregnant should avoid anti-androgen products entirely.

Scientific references

Effects of dietary supplements on androgenetic alopecia: a systematic review and network meta-analysis
Zhou L, Zhu W, Chen Y — Front Nutr, 2025
The Safety and Efficacy of a Proprietary Bioactive Fatty Acids Extract From Saw Palmetto (Serenoa repens) for Promoting Hair Growth and Reducing Hair Loss in Adults With Self-Perceived Thinning Hair: 90-Day Results
Ablon G — J Cosmet Dermatol, 2025
Can we identify a post-Serenoa syndrome (PSS)? A case series on sexual and psychiatric side effects of Serenoa repens
Firenzuoli F, Firenzuoli B, Mascherini V — Br J Clin Pharmacol, 2026

Where to buy

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