Can Finasteride Cause Infertility?
Finasteride can potentially impair fertility in some men, particularly those with pre-existing subfertility, though the evidence for the 1 mg dose remains inconclusive and effects appear reversible upon discontinuation.
Dose-Dependent Effects on Semen Parameters
The impact of finasteride on male fertility varies significantly by dose:
- Finasteride 5 mg/day is definitively associated with reduced semen volume 1
- Finasteride 1 mg/day has inconclusive evidence regarding fertility impact according to the 2024 AUA/ASRM male infertility guidelines 1, 2
- The FDA label notes a 0.6 mL (22.1%) median decrease in ejaculate volume with a concomitant reduction in total sperm per ejaculate, though these parameters remained within normal range 3
Reversibility of Effects
The fertility effects of finasteride appear to be reversible, which is clinically reassuring:
- Clinical trials in healthy volunteers showed no clinically meaningful effects on sperm concentration, mobility, morphology, or pH after 24 weeks of treatment 3
- Parameters returned to baseline with an average time of 84 weeks after discontinuation 3
- Multiple case reports document successful pregnancies and live births after finasteride cessation, including after 10+ years of use 4, 5, 6
High-Risk Populations
Men with pre-existing fertility issues appear more vulnerable to finasteride's effects:
- Case series suggest that finasteride may amplify negative effects in patients with conditions related to infertility, such as varicocele or obesity 7
- Men with baseline oligospermia or impaired spermatogenesis may experience further deterioration while on finasteride 6
- The 2021 AUA/ASRM guidelines acknowledge that data on most risk factors for male infertility, including medications like finasteride, remain limited 1
Mechanism and Clinical Implications
Finasteride inhibits 5-alpha-reductase, converting testosterone to dihydrotestosterone (DHT), which may affect the reproductive system 2:
- Postmarketing reports document male infertility and/or poor seminal quality, with normalization or improvement after discontinuation 3
- Sexual side effects (erectile dysfunction, decreased libido) occur in 2-4% more patients than placebo, which may indirectly impact fertility by affecting sexual function 2, 8, 9
Clinical Recommendations
For men of reproductive age planning pregnancy:
- Consider discontinuing finasteride, particularly in men with pre-existing subfertility or abnormal semen parameters 7, 6
- Allow approximately 84 weeks (though improvement may occur sooner) for complete normalization of semen parameters after cessation 3
- Obtain baseline semen analysis if fertility concerns exist before starting treatment 1
- The 2021 AUA/ASRM guidelines recommend that clinicians may discuss medication-related risk factors with patients, though acknowledging the limited data 1
Important Caveats
- The evidence quality is limited by small case series and the lack of large prospective studies specifically examining fertility outcomes 1
- Healthy men without pre-existing fertility issues may not experience clinically significant effects on spermatogenesis 3, 7
- Animal studies showed slightly decreased fertility in male offspring at approximately 3 times the maximum recommended human dose, though no effects were seen in humans at therapeutic doses 3