Can finasteride (1mg) cause infertility?

Finasteride 1mg and Infertility Risk

Finasteride 1mg does not significantly affect fertility in most men, but may cause temporary and reversible changes in semen parameters that normalize after discontinuation of the medication.

Effects on Male Fertility

• According to the American Urological Association/American Society for Reproductive Medicine 2024 guidelines, finasteride 1mg/day has inconclusive evidence regarding its impact on fertility, while the 5mg dose is associated with reduced semen volume 1
• FDA labeling indicates that treatment with finasteride for 24 weeks in healthy male volunteers revealed no clinically meaningful effects on sperm concentration, mobility, morphology, or pH, though a 0.6 mL (22.1%) median decrease in ejaculate volume was observed 2
• These semen parameter changes remain within normal range and are reversible upon discontinuation of therapy, with an average time to return to baseline of 84 weeks 2
• A double-blind, placebo-controlled multicenter study of 181 men aged 19-41 years found no significant effects of 1mg finasteride daily on sperm concentration, total sperm per ejaculate, sperm motility, or morphology after 48 weeks of treatment 3

Reported Cases and Postmarketing Experience

• The FDA label notes there have been postmarketing reports of male infertility and/or poor seminal quality, with normalization or improvement reported after discontinuation of finasteride 2
• Case reports suggest that finasteride may have more pronounced effects on semen quality in men with pre-existing fertility issues, such as varicocele or obesity 4
• One case report documented successful pregnancy and live birth after the male partner discontinued finasteride following approximately 10 years of use, with semen parameters improving within months after cessation 5

Mechanism of Action and Reproductive Effects

• Finasteride inhibits the 5-alpha-reductase enzyme, which converts testosterone to dihydrotestosterone (DHT), potentially affecting sexual function 6
• Animal studies show that at doses significantly higher than the 1mg human dose, finasteride can affect fertility in rats, but these effects are reversible within 6 weeks of discontinuation 2
• The decrease in fertility observed in animal studies is secondary to effects on accessory sex organs (prostate and seminal vesicles) rather than direct effects on the testes 2

Clinical Considerations and Recommendations

• For men planning pregnancy with their partners, there is no strong evidence supporting the need to discontinue 1mg finasteride 7
• If fertility concerns arise while taking finasteride, discontinuation of the medication may be considered, as semen parameters typically improve after cessation 2, 4, 5
• Men with pre-existing fertility issues or risk factors (such as varicocele or obesity) may be more susceptible to finasteride's effects on semen parameters 4
• Monitoring of semen parameters may be considered in men taking finasteride who are experiencing difficulty conceiving 4, 5

Common Pitfalls and Caveats

• Do not confuse the effects of 1mg finasteride (used for male pattern baldness) with those of 5mg finasteride (used for BPH), as the higher dose has more documented effects on semen volume 1
• Sexual side effects of finasteride (erectile dysfunction, decreased libido) may indirectly affect fertility by impacting sexual function, occurring in approximately 2-4% more patients taking finasteride compared to placebo 8, 6
• The magnitude of sexual dysfunction effect is relatively small compared to natural aging, with finasteride's effect being a mean difference of 3.21 points on sexual function scales, compared to 1.26 points for each year of aging 8
• Discontinuation rates due to adverse events are approximately 6-7% in both finasteride and placebo groups in clinical trials 6