Finasteride (Propecia) side effects
Finasteride (Propecia) · finasteride · by Multiple (Merck originated as Propecia)
Reviewed by the glpzoom Editorial Team against primary clinical sources — FDA labeling, peer-reviewed trials, and specialty-society guidelines.
Content current as of June 2026; updated when guidance or availability changes.
Most common: small (~2-4%) rate of sexual side effects in trials (decreased libido, ED, ejaculation issues). Rare: gynecomastia, mood changes. 'Post-finasteride syndrome' is a contested phenomenon with persistent side effects after discontinuation; baseline rate appears low.
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People also ask
Frequently asked
What are the most common Finasteride (Propecia) side effects?+
Most common: small (~2-4%) rate of sexual side effects in trials (decreased libido, ED, ejaculation issues). Rare: gynecomastia, mood changes. 'Post-finasteride syndrome' is a contested phenomenon with persistent side effects after discontinuation; baseline rate appears low.
How long do Finasteride (Propecia) side effects last?+
Most GI side effects (nausea, constipation) peak in the first 4-8 weeks of dose escalation and improve as the body adapts. Severe or persistent symptoms warrant a clinician call.
When should I stop Finasteride (Propecia)?+
Stop and contact a clinician for severe abdominal pain, persistent vomiting, signs of pancreatitis, gallbladder symptoms, or any reaction outside the expected GI profile.