Supplements
Does Saw Palmetto Lower Testosterone?
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed August 20265 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
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No trial has shown saw palmetto changing the testosterone a blood test reports. Its one clearly measured effect was on DHT, the stronger hormone testosterone converts into, and that was found inside prostate tissue rather than in blood. For urinary symptoms, Cochrane found little to no benefit.
Not sure which markers you need? Build your test →You started saw palmetto for your hair, or for the trips to the bathroom at 3am. Then somebody on a forum said it tanks your testosterone. Now you want to know whether that is true.
The trial record is clearer than the forum. Here is what it says.
1. What is saw palmetto, and why do men take it?
Saw palmetto is an extract from the berries of a small palm tree. It is sold as a food supplement, most often at 320 mg a day.
Men buy it for two things. Urinary symptoms from an enlarged prostate, and hair loss.
Both rest on the same idea. Saw palmetto is thought to slow 5-alpha-reductase, the enzyme that converts testosterone into DHT. DHT, or dihydrotestosterone, is a stronger androgen than testosterone itself. It is the one linked to male pattern hair loss and to prostate growth. So the theory is neat. The question is whether it holds up.
2. Does saw palmetto lower testosterone?
No study has shown that it does.
The careful work on how it acts looked inside the prostate, not in blood. A randomised trial published in Urology in 2001 took biopsies after six months of treatment. DHT in prostate tissue fell by a median of 32%.
That is a tissue reading. It is not the number your blood test prints.
Nobody has shown saw palmetto meaningfully moving serum testosterone in either direction. So if you take it and your testosterone comes back low, the supplement is an unlikely culprit. Age, sleep, weight, illness and the time of your sample all move it more. Our guide to testosterone levels by age shows what the typical range looks like across a life.
3. What did the biggest trials find?
Cochrane pooled 27 studies and 4,656 men in its 2023 review. The conclusion was blunt.
“Serenoa repens alone provides little to no benefits for men with lower urinary tract symptoms due to benign prostatic enlargement.”
— Cochrane review of Serenoa repens, 2023
The largest single trial says the same. CAMUS randomised 369 men to rising doses of saw palmetto or placebo over 72 weeks. Symptoms improved in both arms by about the same amount.
On hair loss, the NCCIH, the US National Institutes of Health's complementary health agency, is short: the evidence is too limited to allow conclusions to be reached. Not disproved. Just not shown.
4. Does saw palmetto change your blood results?
Two things are worth knowing before you book a test.
The first is PSA. The same US centre reports that saw palmetto does not appear to affect PSA levels. That is useful. Some prostate medicines cut PSA roughly in half, which makes the result harder for a clinician to read.
The second is timing, and it matters more than the supplement. Testosterone peaks in the early morning and drifts down through the day. An afternoon sample reads lower on the same man.
Plenty of other pills do interfere with a blood test. Biotin and high dose vitamins are the usual offenders. We cover them in our guide to supplements that affect blood tests.
5. Which markers answer the question
If the real worry is whether your testosterone is low, measure it. One total testosterone figure will not settle it on its own. SHBG is the protein that binds testosterone and holds it out of use, so it decides how much of your total you can actually access.
Helvy's Complete Male Hormones panel (£119) reports total testosterone, free testosterone, SHBG, LH, FSH, prolactin, DHEA-S, free androgen index and albumin.
One honest limit. DHT is not part of this test, and no Helvy panel reports it. If a clinician wants DHT measured, that is a separate step to take with them.
One more. A single low morning reading does not establish anything. Clinicians look for repeated morning results before drawing conclusions. To pick your own markers, the build-my-test tool walks you through it.
READY TO TEST?
Stop guessing what the supplement is doing
Helvy's home blood tests report your male hormone markers with the free fraction and SHBG beside the total, and a written read of what they show. Samples are processed by UKAS-accredited UK labs.
Frequently asked questions
Does saw palmetto lower testosterone?
No study has shown it moving serum testosterone in either direction. The measurable effect found in trials was on DHT inside prostate tissue, which is a different hormone in a different place from the testosterone your blood test reports.
Does saw palmetto block DHT?
Partly, in prostate tissue. A randomised trial in Urology in 2001 found a median 32% fall in prostate DHT after six months. What that means for hair or symptoms is still unsettled.
Does saw palmetto work for an enlarged prostate?
The 2023 Cochrane review of 27 studies and 4,656 men concluded that saw palmetto alone provides little to no benefit for lower urinary tract symptoms. The CAMUS trial of 369 men found the same thing over 72 weeks.
Does saw palmetto affect a PSA test?
NCCIH, the US National Institutes of Health's complementary health agency, reports that it does not appear to affect PSA levels. Helvy does not measure PSA, so that is a test to arrange with your GP.
Does saw palmetto help hair loss?
The same US centre says the evidence is too limited to allow conclusions to be reached. If your hair is thinning, ferritin and thyroid markers are worth checking, because both have a much better established link.
Should I stop saw palmetto before a blood test?
There is no evidence it distorts a male hormone panel, so there is no need to. Book a morning sample instead, because the time of day moves testosterone far more than the supplement does. Never stop something a clinician prescribed without asking them.
Related guides
Testosterone Levels by Age
What a typical range looks like across a life.
SHBG Blood Test UK
The protein that decides how much testosterone you can use.
Does Testosterone Cause Hair Loss?
The DHT question, from the other direction.
Low Testosterone Symptoms in Men
What low testosterone actually feels like.
Does Zinc Increase Testosterone?
Another supplement claim, weighed against the trials.
Supplements That Affect Blood Tests
The pills that really do distort a result.