Does Viagra Affect Sperm?

Standard doses of sildenafil (Viagra) do not appear to harm sperm in healthy men. The available clinical evidence shows no meaningful effect on sperm count, movement or shape at the doses most men take.

What the main clinical study found#

The most-cited human trial was published in the British Journal of Clinical Pharmacology by Purvis, Muirhead and Harness (2002). Seventeen healthy men each received a single 100mg dose of sildenafil and a placebo, in a randomised crossover design. Sperm count, motility, density, morphology and vitality were measured afterwards. None of the parameters changed in a statistically significant way.

The trial also measured how much sildenafil passed into semen. The amount was very small. This matters for men who worry about whether trace sildenafil in semen could affect a female partner or a fertilised egg. The quantities detected were far too low to cause concern.

One honest caveat: 17 participants is a small sample, the study tested a single dose rather than long-term use, and it was funded by Pfizer. That does not make the results wrong, but it does mean the evidence base is thinner than the reassuring headlines suggest.

Does long-term sildenafil use matter?#

No long-term human trials have followed men taking sildenafil regularly and tracked their fertility outcomes. Everything published in healthy volunteers uses single acute doses. So while the short-term picture looks fine, nobody can say with certainty what years of regular use does to sperm parameters. For most men trying to conceive, this is probably not a practical concern. Sildenafil clears the body within 24 hours and does not accumulate.

The acrosome question#

Some lab studies have raised a question about sperm DNA and the acrosome. The acrosome is a cap on the sperm's head. It has to stay intact until the sperm reaches the egg, then release enzymes to help penetrate it. A few in vitro studies suggest that sildenafil at high concentrations can trigger this release too early, called a premature acrosome reaction.

The important word there is high concentrations. The levels used in lab studies were far greater than what reaches sperm after a normal oral dose. Whether this happens at real-world semen concentrations is unclear, and no human study has shown it causes a problem in practice.

Sperm DNA fragmentation is another marker some fertility specialists use. There is no convincing clinical evidence linking standard sildenafil doses to increased DNA fragmentation in human semen.

ED and fertility often share the same root cause#

If you have ED and are struggling to conceive, the sildenafil is unlikely to be the problem. Conditions like diabetes, obesity and cardiovascular disease can reduce both erection quality and sperm production. Sildenafil treats the erection but does nothing for the underlying condition affecting sperm.

This is worth raising with your GP, especially if you are self-medicating with Viagra Connect (available over the counter in 50mg) without a clinical review. Men in this situation may have an undiagnosed condition affecting their fertility that nobody has investigated.

Getting a semen analysis on the NHS#

NICE guideline CG156 on fertility recommends that men who have been trying to conceive for 12 months without success should be offered investigation, including a semen analysis. Your GP can refer you for this. The analysis looks at sperm count, motility, morphology and volume, using WHO 2021 reference values.

If you would rather not wait, private semen analysis is available from andrology clinics across the UK. Costs vary depending on the clinic and what the test includes, so check directly with providers for current pricing.

If your results come back normal, sildenafil is almost certainly not a factor in any difficulty conceiving. If the results show a problem, the focus shifts to what is causing it, and sildenafil is far down the list of suspects.

For men who want to talk through their sildenafil use more generally, the Totiva ED service offers clinician-reviewed treatment and a free online consultation. You might also find the guide on how to take Viagra safely and effectively useful for dosing questions.