Does Viagra affect sperm? Not in healthy men, on the evidence so far. In placebo-controlled studies, a single dose of sildenafil, the medicine in Viagra, made no difference to sperm count, movement (motility) or shape (morphology). In men with fertility problems, some studies found that sperm moved slightly better after a dose. The one warning of harm came from sperm exposed to sildenafil in a laboratory dish, not from men taking the tablet.
What does the Viagra label say about sperm and fertility?
It reports no harm. "There was no effect on sperm motility or morphology after single 100 mg oral doses of sildenafil in healthy volunteers", and "No relevant adverse effects were found in reproduction studies in rats and rabbits" (EMA — Viagra product information). Only a trace reaches the semen: less than 0.0002% of a 100 mg dose, 90 minutes after taking it. The label reports single doses only and makes no claim about the chance of conception. The Australian leaflet says nothing about sperm (Viagra CMI).
What did studies in healthy men find?
No change. In a crossover study of 17 healthy men, a 100 mg dose had no significant effect on sperm motility, count, abnormal forms or the share of living sperm, or on the volume of the ejaculate (Purvis et al., Br J Clin Pharmacol 2002). In a placebo-controlled trial of 20 men with proven fertility, 100 mg made no difference to the semen (Aversa et al., Hum Reprod 2000); the same trial timed how soon the men could have another erection — see can Viagra shorten the refractory period? In 20 men taking 50 mg, the standard semen measures did not change either, though some measures of how fast sperm swam went up (du Plessis et al., Fertil Steril 2004).
Does Viagra improve sperm in men with fertility problems?
Slightly, in some studies. A 2017 meta-analysis pooled 11 studies with 1,317 men. After a PDE5 inhibitor, the class that includes sildenafil and tadalafil, the share of moving sperm rose "only in infertile men but not in normal patients", as did the share of normally shaped sperm; semen volume, sperm concentration and hormone levels did not improve. The authors' conclusion: the tablets "could modestly increase the sperm motility and morphology in infertile men" (Tan et al., Urology 2017). It measured sperm, not pregnancies. A 2023 review adds that "the best-controlled studies suggested no change in the sperm quality" (Mostafa et al., Sex Med Rev 2023).
Where does the worry about a "premature acrosome reaction" come from?
From a laboratory study. Researchers at Queen's University Belfast added sildenafil directly to sperm samples from 57 men at a fertility clinic. More sperm swam forward, and faster, but more had also gone through the acrosome reaction early — 22.1% against 11.8% without sildenafil in the better-quality sperm — and the authors concluded that it "may adversely affect male fertility" (Glenn et al., Fertil Steril 2007). In men who swallowed a 50 mg tablet, the acrosome reaction was unchanged (du Plessis et al.). A result in a dish is not a result in the body.
Is Cialis (tadalafil) any different?
Its label carries a line Viagra's does not. In two of three studies of daily tadalafil lasting 6 to 9 months, sperm count and concentration fell — changes "of unlikely clinical relevance", with no change in motility or shape — and the fertility section notes that "a decrease in sperm concentration was seen in some men" (EMA — Cialis product information). In the 9-month study of daily 20 mg in men aged 45 and over, concentration fell by half or more in 12 of 95 men on tadalafil and 2 of 96 on placebo; in 8 of the 12 it recovered within six months of stopping (Hellstrom et al., Eur Urol 2008). In one small study of 18 young men with fertility problems, a single dose of tadalafil lowered sperm motility where sildenafil raised it (Pomara et al., Fertil Steril 2007). The medicines are compared on everything else in Viagra vs Cialis vs Levitra.
What does lower sperm quality, and how is it checked?
Healthy Male lists hormone problems, varicocele, testicular injury, severe illness, obesity, opiates, some medications, and testosterone therapy or anabolic steroids, which reduce sperm production; ejaculation problems and erectile dysfunction can also cause male infertility. A doctor checks with a semen analysis or hormone blood test and an examination, and a couple who have not conceived after a year of trying should both see one (Healthy Male). More in can erectile dysfunction cause low sperm count? and can testosterone and Cialis be taken together? Trying for a baby when erections are a problem is covered in can Viagra affect male fertility and the chances of conception?
The short answer
A single dose of Viagra did not change sperm count, motility or shape in healthy men. In men with fertility problems, studies found a modest improvement in how sperm move, not a proven gain in pregnancies. The laboratory warning was not seen in men who took a tablet. Daily tadalafil lowered sperm concentration in some men. More on how sildenafil works is in our guide to how well Viagra works and how long it lasts.
