Saw palmetto side effects: like finasteride?

Saw palmetto’s listed side effects are mild: stomach pain, nausea and headache. A few people report sexual and mental changes that can last after stopping, much like post-finasteride syndrome, or PFS.

PFS is more than sexual problems. The 2022 criteria say problems with thinking, depression and suicidal thoughts can come with or without sexual changes, and they name saw palmetto as a possible trigger.

Saw palmetto is a berry extract taken for the prostate and for hair, sometimes inside a multivitamin. In the UK it’s sold as a supplement, and some products are registered as traditional herbal medicines for prostate symptoms. The EU’s 2015 list of its side effects doesn’t mention sex or mood.

Imraan is a doctor, an anaesthetist. He took a common multivitamin that happened to contain saw palmetto. Watch it to hear how he came to link a multivitamin with what followed.

Play video: Imraan's story, saw palmetto in a multivitamin

The film’s description sets out what followed. Sexual problems came first, then severe insomnia, emotional blunting, trouble with cognition and intolerance to some foods.

What are the side effects of saw palmetto?

Mostly mild ones, such as stomach pain. The EU’s herbal medicines committee wrote the official summary for saw palmetto medicines in 2015. For the best-studied extract, it lists stomach pain and headache as common, and nausea, raised liver enzymes and a skin rash as uncommon.

Breast swelling in men, which doctors call gynaecomastia, is listed as uncommon and reversible, under hormone disorders. The UK leaflet for finasteride lists breast swelling too.

In trials, people on saw palmetto had about as many side effects as people on a dummy pill. A 2023 Cochrane review pooled 27 trials and found little to no difference. In the trials the EU assessed that scored sexual function, saw palmetto made no clear difference compared with a dummy pill.

Does saw palmetto work like finasteride?

Possibly, but the evidence is mixed, going by the EU’s 2015 assessment. In the lab, saw palmetto extracts block 5-alpha-reductase, the enzyme that turns testosterone into a stronger hormone, DHT. Finasteride works by blocking it too.

In the lab it took far higher strengths than finasteride needs, the EU assessment notes. In one small study, a week of saw palmetto didn’t lower DHT in the blood, while finasteride did. Another small study found lower DHT in prostate tissue removed during surgery.

The EU summary puts it plainly: “The mechanism of action is not known.”

Does saw palmetto block the finasteride enzyme?

In the lab

Yes, at high strengthsExtracts block both forms of the enzyme.

In the blood

No change seenOne week, in healthy volunteers.

In the prostate

Lower DHTOne small study, after three months.

The EU verdict

Not knownHow it works in people is still unclear.

Can saw palmetto side effects last after stopping?

Some people report that they do. In 2022, doctors and researchers who proposed criteria for PFS and related conditions named saw palmetto alongside finasteride and dutasteride as a possible trigger. They added that how often these conditions happen is unknown.

In 2026 a team in Florence published a case series. People who had posted on an Italian PFS forum were assessed at the team’s clinic. Their report describes sexual, psychiatric and physical symptoms. These had lasted nearly five years on average, and only three people had fully recovered. The patients came through a forum, so the study can’t say how often this happens.

Some of them had also taken finasteride. Those on both were more severely affected, the authors say. They suggest the idea that saw palmetto is completely safe may keep people from reporting it.

The UK leaflet for finasteride warns that erection and sex drive problems can persist “after discontinuation of treatment”. Saw palmetto’s official documents carry no such line. For some people the symptoms have lasted years after stopping. Nobody knows yet who will be affected, or whether it will ease. Our page on what PFS feels like shows the symptoms people describe.

What can I do?

Saw palmetto is a supplement, so there’s often no prescriber. Whether you take it is your decision; a GP or pharmacist can talk it through with you. Registered herbal medicines carry a leaflet, so read it, and check multivitamin labels for “saw palmetto” or “Serenoa repens”.

If something changed, tell your GP and give your dates. You could open with: “I think a supplement may have caused this, and it hasn’t stopped.”

Many people say it took time to be taken seriously. You can report it without a doctor agreeing. Our guide to which doctor to see about PFS may help.

Report it: it helps everyone

A doctor’s note helps you. A report to the medicines regulator helps everyone else: it is how patterns get noticed.

• No proof needed. A suspicion is enough, even years after stopping.
• Where: the Yellow Card scheme in the UK, which also takes reports on herbal medicines. In the US it’s MedWatch.
• Use the right words. Name the product and say the symptoms continued after stopping. The term for PFS is Post 5-alpha-reductase inhibitor syndrome (MedDRA 10082430).

Our reporting guide walks you through it

What else do people ask?

Does saw palmetto help hair loss? The evidence is too limited to say, according to the US National Center for Complementary and Integrative Health. For an enlarged prostate, the 2023 Cochrane review found it makes little or no difference to symptoms.

Can other supplements do this? There are reports after a few, with almost no research. Our article on other medicines with lasting sexual side effects covers Lion’s Mane and more.

Is it really PFS if I never took finasteride? That’s an open question. The 2022 criteria include saw palmetto, and the Florence team asks whether it is a “post-Serenoa syndrome” of its own. The symptoms overlap with PFS, and for now that’s where people find each other.

Imraan is a doctor, and even he didn’t know at first that a multivitamin could be linked to this. If anything changed after saw palmetto, report it: a report counts even years later.

Sources

1. Committee on Herbal Medicinal Products (HMPC), European Medicines Agency. European Union herbal monograph on Serenoa repens (W. Bartram) Small, fructus, EMA/HMPC/280079/2013, adopted 24 November 2015. Section 4.8 (well-established use, hexane extract): common, abdominal pain and headache; uncommon, nausea, increase of transaminases or gamma-glutamyltransferases, skin rash, “reversible gynecomastia”. No sexual side effect is listed in either the well-established or the traditional-use column. Traditional use: “exclusively based upon long-standing use”. Section 5.1: “The mechanism of action is not known.” Male adults only.
2. HMPC, European Medicines Agency. Assessment report on Serenoa repens (W. Bartram) Small, fructus, EMA/HMPC/137250/2013, 24 November 2015. Section 1.2 (regulatory status overview): United Kingdom, “TRAD registration”. Section 3.1.1.1.1: extracts inhibit 5-alpha-reductase in vitro. Section 3.4: concentrations needed were “much higher (up to 1000x)” than for pure substances such as finasteride. Section 4: Strauch and colleagues, 1994, 32 healthy volunteers for one week, no change in serum DHT on a 320 mg hexane extract, while finasteride lowered it; Di Silverio and colleagues, 1998, 25 men with BPH, lower DHT in prostate tissue after three months. Clinical trials in its tables that measured sexual function showed no clear difference from placebo. Section 5.3.3: reversible gynaecomastia observed rarely.
3. HMPC, European Medicines Agency. Addendum to assessment report on Serenoa repens, EMA/HMPC/602363/2019, 7 July 2021. EudraVigilance search 2015 to March 2021: 641 reports mentioning Serenoa; most often gastro-intestinal, skin, headache and gynaecomastia; no revision of the monograph.
4. Franco JVA, Trivisonno LF, Sgarbossa N and colleagues. Serenoa repens for the treatment of lower urinary tract symptoms due to benign prostatic enlargement: an updated Cochrane review. World J Mens Health 2024;42(3):518-530 (summary of the 2023 Cochrane review). 27 studies, 4,656 participants. Saw palmetto “probably results in little to no difference in adverse events” (moderate certainty), and “results in little to no difference” in urinary symptoms and quality of life (high certainty). Read from the abstract.
5. Healy D, Bahrick A, Bak M and colleagues. Diagnostic criteria for enduring sexual dysfunction after treatment with antidepressants, finasteride and isotretinoin. Int J Risk Saf Med 2022;33(1):65-76. “Finasteride, dutasteride and saw palmetto are 5 alpha-reductase inhibitors that can trigger an enduring sexual dysfunction with a very similar profile to PSSD.” “The incidence of these conditions is unknown.” An expert consensus.
6. Firenzuoli F, Firenzuoli B, Mascherini V and colleagues. Can we identify a post-Serenoa syndrome (PSS)? A case series on sexual and psychiatric side effects of Serenoa repens. Br J Clin Pharmacol 2026;92(4):1237-1246. Cases from self-reports on an Italian post-finasteride syndrome forum, each followed by a structured clinical evaluation at the CERFIT centre, Florence. Doses 120 to 900 mg a day; onset within a month in 61%; symptoms “severe and persistent (mean duration 4.7 years)”, complete remission in only three patients; causality “probable” in 54% on the Naranjo scale; combined use with finasteride linked to greater severity and persistence. Read from the abstract via Europe PMC; the number of patients is not given there.
7. US National Center for Complementary and Integrative Health, Saw palmetto, last updated April 2025. Hair loss: “The evidence is too limited to allow conclusions to be reached.” Adverse effects “mild and infrequent”.
8. Moral Medicine, interview with Imraan (21 minutes 24 seconds). The details in the text follow the channel’s description of the interview, which says his symptoms overlap with those of post-finasteride syndrome. Captions could not be read (21 October 2026); our story page already plays this film. His story on our site: Imraan’s story: saw palmetto in a multivitamin.
9. Propecia 1 mg film-coated tablets, patient leaflet (UK, EMC 2194), as read on 21 October 2026. Section 4, frequency unknown: “breast swelling or tenderness”; also “persistent difficulty having an erection”, “persistent decrease in sex drive” and “persistent problems with ejaculation”, each “after discontinuation of treatment”.
10. MHRA, Yellow Card, as read on 21 October 2026. Reports can be made for suspected side effects to all medicines, including “herbal medicines and homeopathic remedies”.
11. MHRA, Prostasan Saw Palmetto Capsules, product information on the MHRA products site (THR 13668/0011), as read on 22 October 2026. One example of a UK traditional herbal registration. Summary of product characteristics, text revised 5 February 2020. Section 4.1: “Traditional herbal medicinal product used for the relief of lower urinary tract symptoms in men”. It is for men with confirmed benign prostatic hypertrophy (BPH), “based on traditional use only.” Section 4.8 lists belching, gastrointestinal discomfort and allergic reactions such as rash, frequency not known; no sexual side effect is listed.