Does Saw Palmetto Increase Testosterone? What the Evidence Actually Shows

Saw palmetto is one of the UK's most widely taken herbal supplements, often marketed as a natural way to support male hormonal health, prostate function, and even sexual performance. But does it actually increase testosterone? The short answer is: probably not in any clinically meaningful way, and certainly not reliably enough to treat conditions like erectile dysfunction.

Here's what the research shows, and what that means if you're taking saw palmetto or thinking about starting it.

What Saw Palmetto Actually Does in the Body#

Saw palmetto comes from the berries of Serenoa repens, a small palm tree native to the southeastern United States. The extract contains a mix of fatty acids, plant sterols, and flavonoids. Its main proposed mechanism of action is inhibiting 5-alpha-reductase, the enzyme that converts testosterone into dihydrotestosterone (DHT).

DHT is a more potent androgen than testosterone itself. It plays a key role in prostate growth and male pattern hair loss. By slowing down this conversion, saw palmetto theoretically leaves more free testosterone circulating in the body and less DHT being produced.

This is the same basic mechanism as finasteride, a prescription-only medicine used for benign prostatic hyperplasia (BPH) and androgenetic alopecia. The difference is that finasteride has been through rigorous clinical trials and is licensed for these indications in the UK. Saw palmetto has not, and that distinction matters.

Does It Actually Raise Testosterone Levels?#

The honest answer is that the evidence is weak and inconsistent.

One older review published in the Journal of the International Society of Sports Nutrition found that men taking saw palmetto over a two-week period had marginally higher testosterone levels than those in a placebo group. Sounds promising, but this finding has not been reliably replicated in well-designed subsequent trials.

What's more, any increase in measurable testosterone from blocking 5-alpha-reductase is a downstream effect, not a direct hormonal stimulus. Saw palmetto doesn't stimulate the testes to produce more testosterone. It may simply reduce how quickly some of that testosterone is converted to DHT. Whether that translates into any meaningful physiological benefit for most men is a separate question, and the research hasn't confirmed it does.

A 2011 double-blind, randomised study involving 369 men compared saw palmetto at up to three times the standard daily dose (160mg twice daily is the typical recommendation) against a placebo for BPH symptoms. The saw palmetto group showed no significant benefit over placebo. Larger, well-controlled trials have consistently found similarly underwhelming results.

Saw Palmetto, Libido, and Erectile Dysfunction#

This is where things get particularly thin on evidence.

Some proponents suggest that by preserving more free testosterone, saw palmetto might support libido and sexual function. In theory, lower DHT and higher free testosterone could improve sex drive. In practice, there is no good clinical trial evidence that saw palmetto improves erectile function, libido, or sexual satisfaction in men.

Saw palmetto is not licensed in the UK for the treatment of erectile dysfunction. It is not recommended by NICE or mentioned in the BNF as a treatment option for ED. The regulatory position is clear: saw palmetto is classified as a food supplement under UK law, not a medicine. This means manufacturers are not required to prove efficacy before selling it, which is a significant distinction from prescription treatments.

For men dealing with ED, it's worth understanding that the condition usually has a physiological root cause, most commonly reduced blood flow to the penis caused by endothelial dysfunction. This is not something an herbal supplement that mildly influences enzyme activity is going to fix. ED is also increasingly recognised as a marker of underlying cardiovascular risk, which is another reason it warrants proper clinical assessment rather than self-treatment with supplements.

If you're looking for treatments that have a strong evidence base for erectile dysfunction, our ED service at Totiva covers licensed options prescribed by UK-registered clinicians.

The BPH and ED Overlap#

One group of men where saw palmetto comes up particularly often is those with benign prostatic hyperplasia. BPH and erectile dysfunction frequently co-exist, especially in men over 50. Lower urinary tract symptoms can affect sleep, cause anxiety, and indirectly dampen sexual confidence. So it's understandable that men managing BPH symptoms might hope saw palmetto addresses both issues at once.

The evidence on saw palmetto for BPH is mixed. A Cochrane systematic review concluded that Serenoa repens was no more effective than placebo for improving urinary symptom scores or flow rates in men with BPH. More recent meta-analyses have found modest benefits for some symptom outcomes with specific hexanic extracts, but these results are not consistent across all formulations.

Critically, if you're taking saw palmetto for BPH symptoms, it's important to tell your GP. Saw palmetto can lower PSA (prostate-specific antigen) levels, which is a blood marker used to screen for prostate cancer and monitor BPH. If your GP doesn't know you're taking it, a falsely reassuring PSA reading could delay the detection of something more serious. This is one of the more underappreciated clinical concerns with saw palmetto use.

Does Saw Palmetto Help with Hair Loss?#

This is another area where saw palmetto is frequently marketed. Because it inhibits 5-alpha-reductase and reduces DHT, the logic follows that it might slow male pattern hair loss, since DHT is a key driver of follicle miniaturisation in androgenetic alopecia.

Small studies have shown modest results, and saw palmetto is sometimes compared informally to low-dose finasteride. One 2014 randomised study found some benefit for hair count over 24 weeks. However, the evidence base is substantially weaker than for finasteride, which has decades of controlled trial data behind it and is licensed for this indication.

If hair loss is your primary concern, finasteride (and topical minoxidil) have considerably stronger evidence and regulatory backing in the UK.

Side Effects and Drug Interactions You Should Know About#

Because saw palmetto is sold as a supplement rather than a medicine, many people assume it's harmless. It isn't without risk.

Reported side effects include:

• Nausea, diarrhoea, and stomach discomfort (particularly when taken without food)
• Headaches and dizziness
• Reduced libido in some users (counterintuitively, given why many people take it)
• Breast tenderness
• Potential effects on bleeding time

The bleeding risk is worth taking seriously. Saw palmetto may have mild antiplatelet effects, meaning it could increase bleeding tendency. If you're taking anticoagulants such as warfarin, or antiplatelet drugs like aspirin or clopidogrel, you should speak to your GP or pharmacist before taking saw palmetto. The interaction is not extensively characterised, but the theoretical risk is real.

For men taking sildenafil or tadalafil for erectile dysfunction, there is no well-documented direct pharmacokinetic interaction with saw palmetto. However, if you're using saw palmetto alongside PDE5 inhibitors and notice unexpected side effects, it's worth discussing with a pharmacist.

Quality control is another concern. Saw palmetto supplements are not subject to the same manufacturing standards as licensed medicines in the UK. The concentration of active compounds varies considerably between brands. A product claiming 160mg of saw palmetto extract may contain very different levels of the fatty acids thought to drive its effects, depending on the extraction method and standardisation process used. If you do choose to take it, look for products with a Traditional Herbal Registration (THR) mark from the MHRA, which at least indicates the product has been assessed for quality and safety (though not efficacy).

What Actually Works for Erectile Dysfunction#

For men looking for reliable, evidence-based treatment for ED, the picture is much clearer than with herbal supplements.

PDE5 inhibitors are the first-line treatment recommended by NICE and detailed in the BNF. They work by relaxing smooth muscle and increasing blood flow to the penis in response to sexual stimulation. The main options available in the UK include:

Sildenafil is the most widely prescribed ED medication and contains the same active ingredient as Viagra. It's taken as needed, typically 30 to 60 minutes before sexual activity, and is effective in around 70% of men. Generic sildenafil is now available on the NHS and privately at very affordable prices. At Totiva, sildenafil 50mg is available from £4.99 for four tablets.

Tadalafil offers more flexibility. The as-needed version (10mg or 20mg) lasts up to 36 hours, earning it the nickname "the weekend pill". A lower-dose daily version (2.5mg or 5mg) is taken every day and provides continuous coverage, which suits men who prefer not to plan around medication. At Totiva, daily tadalafil starts from £9.99 for 28 tablets.

Viagra Connect and Cialis Together are branded over-the-counter versions of sildenafil 50mg and tadalafil 10mg respectively, available without a prescription from pharmacies.

Beyond medication, lifestyle factors play a significant role. Regular aerobic exercise, stopping smoking, reducing alcohol, improving sleep, and managing cardiovascular risk factors (blood pressure, cholesterol, blood sugar) all have genuine evidence behind them for improving erectile function. ED is often a vascular problem, and anything that's good for your heart tends to be good for your erections.

Psychological contributors to ED are also common and often overlooked. Performance anxiety, relationship stress, depression, and low self-esteem can all either cause or worsen erectile difficulties. In these cases, psychosexual therapy or cognitive behavioural therapy may be more appropriate than medication alone.

Telling Your GP About Supplement Use#

If you're currently taking saw palmetto, or any herbal supplement, and you're also seeing a GP or specialist for BPH or ED, make sure to mention it at your next appointment. This matters for a few reasons.

First, the PSA issue described above. Second, any potential interactions with prescribed medicines. Third, your GP can help you weigh up whether the supplement is providing genuine benefit or whether switching to a licensed treatment would be more appropriate for your situation.

It's sometimes tempting to avoid mentioning supplements because they feel more "natural" and less like something that needs disclosing. But from a pharmacist's perspective, anything that affects your hormones or enzyme activity is worth flagging.

Getting Proper Support for ED#

If erectile dysfunction is your main concern, the most useful thing you can do is get a proper assessment rather than relying on supplements with uncertain evidence. ED is treatable in the vast majority of cases, and there's no reason to persist with something that isn't working.

Totiva's online consultation for ED is free, and you only pay if a treatment is approved for you. There's no need for an in-person GP visit, no subscription required, and treatments are delivered discreetly. It's a straightforward way to access the same licensed medications your GP would prescribe, reviewed by UK-registered clinicians.

If you'd like to explore your options, you can start a free ED consultation with Totiva today.