Can You Take Saw Palmetto With Tamsulosin, Finasteride or Blood Thinners?

By Alice Hess
Published October 21, 2026 · Reading time about 12 minutes

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This is the question of a man who already takes a prescription and is looking at the supplement aisle. The honest answer is different for each of the three medicines men over 50 most often ask about, so this guide takes them one at a time: what is recorded, what has actually been tested together, and what those tests found. If you are still sorting out what your symptoms mean, start with our guide to enlarged prostate symptoms.

What do official sources say about saw palmetto interactions?

Less than you might expect. The National Center for Complementary and Integrative Health (NCCIH) says saw palmetto is well tolerated, has been used safely in studies for up to 3 years, and has mild, infrequent side effects such as digestive symptoms, dizziness and headache. It does not list a specific drug interaction. Its general advice: "If you take any type of medicine, talk with your health care provider before using any herbal product; some herbs and medicines interact in harmful ways."¹

"No interaction listed" is not the same as "no interaction possible." It mostly means few combinations have been studied. That is why the useful question is not "is it dangerous?" but "has anyone tested this pair, and what did they find?" The table below answers that for the three medicines men ask about most.

Saw palmetto with prostate medicines and blood thinners: the evidence side by side

Can you take saw palmetto with tamsulosin (Flomax)?

This pair has actually been tested, twice.

The OCOS trial (France, 2002)

A double-blind trial randomized 329 men with moderate to severe symptoms (IPSS of 13 or more) to tamsulosin 0.4 mg once a day plus either saw palmetto 160 mg twice a day or a placebo, for 52 weeks. Symptom scores improved by 5.2 points with tamsulosin alone and 6.0 points with the combination, a difference that was not statistically significant (p = 0.286). Flow rate, quality of life and safety did not differ either. The authors concluded that adding saw palmetto "did not provide any significant benefit."⁵

A smaller Turkish study (2007)

Sixty men were split into three groups of 20: saw palmetto 320 mg a day, tamsulosin 0.4 mg a day, or both. The groups did not differ in flow improvement or symptom score improvement, and the authors wrote that the combination "does not provide extra benefits." No adverse effect was detected in the saw palmetto group.⁴ Twenty men per group is too small to prove safety, so read this as a hint, not a guarantee.

What this means for you

The combination does not look dangerous in these trials, but it also did not add anything. Putting the 0.8-point difference from OCOS next to the roughly 3-point change men can feel on the IPSS puts it in perspective.^5,11 Side effects of tamsulosin itself, such as dizziness and ejaculation problems, came up in saw palmetto studies that used tamsulosin as a co-treatment, which the 2023 Cochrane review notes are typical of alpha blockers.² If you are on tamsulosin and feel dizzy, that is more likely the tamsulosin. Our guide to natural alternatives to Flomax covers the options that have been compared with it directly.

Can you take saw palmetto and finasteride together?

We did not find a randomized trial that tested saw palmetto added to finasteride or dutasteride for an enlarged prostate. Two facts matter instead.

They are thought to work on the same pathway

The 2023 Cochrane review lists, among saw palmetto's proposed mechanisms, acting as "a weak surrogate 5-ARI inhibiting the conversion of testosterone to dihydrotestosterone."² Finasteride and dutasteride are 5-alpha reductase inhibitors (5-ARIs), the drug class that the guideline describes as shrinking the prostate.⁹ In other words, saw palmetto is proposed to be a weak version of a medicine you would already be taking at full strength, and no trial shows that adding it helps.

The PSA catch

This is the part most pages get wrong. The AUA guideline (previous version, 2021, amended 2023) explains that 5-ARIs shrink the prostate and lower serum PSA by approximately 50 percent, so the measured PSA of a man on a 5-ARI should be doubled when it is used to track the prostate or screen for cancer.⁹ Saw palmetto does not do this. In the CAMUS trial, 369 men over 45 took placebo or saw palmetto at rising doses of 320, 640 and then 960 mg a day for 72 weeks. PSA changed by 0.16 ng/mL on placebo and 0.23 ng/mL on saw palmetto, a difference that was not significant.¹⁰ The NCCIH agrees that saw palmetto does not appear to affect PSA readings, even at higher-than-usual amounts.¹

So if someone tells you saw palmetto "lowers PSA like finasteride," the trial says otherwise. The practical point: tell whoever orders your PSA test about every prostate medicine and supplement you take. Our guide to PSA testing by age explains how results are read.

Is saw palmetto safe with blood thinners?

Here the evidence is thin in both directions.

The case reports

A 2014 review of herb and warfarin interactions found two reports involving saw palmetto. In one, the INR of a 61-year-old man on warfarin rose modestly from 2.4 to 3.4 after he took a saw palmetto combination product, five tablets a day for six days. In the other, a 53-year-old man had excessive bleeding during surgery to remove a brain tumor.⁷ In that surgical case, published in 2001, his bleeding time was prolonged and returned to normal a few days after he stopped the herb.⁸

The lab and enzyme data

In test tubes, saw palmetto inhibits some liver enzymes that clear drugs, including CYP2C9. But the review notes that clinical studies found no clinically relevant effect, and it rated the saw palmetto and warfarin interaction Level IV, "doubtful," the lowest of its four levels.⁷ In one of those clinical studies, 12 healthy volunteers took 320 mg a day for 14 days with no change in the activity of CYP2D6 or CYP3A4, two enzyme pathways that many common medicines depend on. The authors called it only an initial investigation.⁶

What this means for you

A "doubtful" rating is not a green light. Warfarin is a drug with a narrow therapeutic index, which makes interactions a major safety concern,¹² and two case reports cannot rule out a rare effect. If you take warfarin, apixaban, clopidogrel or daily aspirin, talk to the doctor who manages it before you add any supplement. Tell your surgeon and anesthesia team about every supplement before any operation; the authors of the surgical case report urged doctors to ask about them.⁸

The ingredient most people overlook: ginkgo

Some prostate products are not single-herb saw palmetto but blends of several ingredients, and then the bleeding question can come from a different line on the label. The NCCIH states that "Ginkgo may increase the risk of bleeding in people who are taking anticoagulant drugs, such as warfarin," and that it may interact with other drugs.³ If you take a blood thinner and the label lists ginkgo, that is the ingredient to raise with your doctor first.

The same logic applies to every blend: each added herb is one more interaction to check. Our guide on how to read a prostate supplement label shows how to list every ingredient and dose in about a minute, so you can hand that list to your pharmacist.

Questions to ask your doctor or pharmacist

• Is there any reason this supplement could interfere with my current medicines? (Bring the full label, not just the product name.)
• If I take warfarin: should my INR be checked sooner after I start it?
• If I take finasteride or dutasteride: will you account for that when you read my PSA?
• Do I have surgery or a procedure coming up where I should mention it?
• How will we know if it is working? (Agree on a symptom score before and after.)

Also check the rest of your medicine cabinet. Cold and allergy products are a more common source of urinary trouble than saw palmetto; see cold and allergy medicine with an enlarged prostate. Do not stop or change a prescribed medicine without your doctor.

Does saw palmetto work well enough to be worth the question?

Before weighing interactions, weigh the benefit. The 2023 Cochrane review pooled 27 studies with 4,656 men and concluded that saw palmetto "alone provides little to no benefits" for urinary symptoms from an enlarged prostate. In the most reliable studies, it lowered symptom scores by 0.90 points more than placebo at 3 to 6 months. There was more uncertainty about combinations with other plant extracts.² The NCCIH summarizes the same review: little or no benefit when used alone.¹

For comparison, about 3 points is the smallest drop men notice on the IPSS.¹¹ If you decide to try it anyway, our saw palmetto dosage guide shows the amounts the trials used, our article on how long saw palmetto takes to work covers when to judge it, and prostate supplements vs medication compares the categories side by side.

Where a supplement fits

For a man already on a prostate medicine, a supplement is an add-on, never a swap, and the trials above suggest the add-on rarely adds much. If your doctor agrees it is safe with your prescriptions, choose a product whose label lists every ingredient with its dose, check each one against your medicine list, and judge it by your symptom score after about 12 weeks. No supplement treats, cures or prevents BPH.

Frequently asked questions

About the author

Alice Hess is a health researcher and wellness writer at ProstateClarity. She is not a doctor, a nurse, a nutritionist or any kind of licensed clinician, and nothing here is medical advice. She started this work because of her father: at 76 he was getting up several times a night, and the research she did for him helped him get back to sleeping through the night. One man's story is not evidence, which is why every guide here is built on published research. She reads labels, primary research and regulatory limits, and publishes the numbers manufacturers leave out. More about her work and how these articles are researched.

Found an error? Write to contact@prostateclarity.com with the sentence and the source that contradicts it. Corrections are made in the article with the date noted.