Finasteride can help male pattern hair loss, but choosing it includes understanding its risks. This page separates first-year trial rates from later safety reports, explains PSA changes and gives clear steps for concerning symptoms.
In the first year of the Propecia trials, one or more of decreased libido, erectile dysfunction or ejaculation disorder was reported by 3.8% of 945 men taking finasteride and 2.1% of 934 taking placebo. These are first-year combined rates, not five-year rates or the frequency of symptoms persisting after treatment.
The absolute difference was 1.7 percentage points, or about 17 additional reports per 1,000 participants. That trial difference does not predict what will happen to any one person. Individual rates were decreased libido 1.8% versus 1.3%, erectile dysfunction 1.3% versus 0.7%, and ejaculation disorder 1.2% versus 0.7%. See section 6.1 of the label.
Current U.S. labeling includes depression and suicidal thoughts or behavior among postmarketing reports; their frequency cannot be calculated from those reports. EMA's 2025 review advises stopping finasteride 1 mg and seeking medical advice for depression or suicidal thoughts. If you may act on those thoughts or cannot stay safe, seek emergency help immediately. Discuss pre-existing mood concerns before starting.
Breast tenderness or enlargement has been reported. Contact a clinician promptly for a new lump, pain, enlargement or nipple discharge. Do not assume every breast change is a harmless medication effect; an examination may be needed.
Persistent sexual symptoms after stopping finasteride, including erection, libido, ejaculation and orgasm problems, are included in postmarketing labeling. The term post-finasteride syndrome is sometimes used for persistent sexual and other complaints. Its mechanisms and frequency remain uncertain; the original trial rates do not quantify this risk.
Persistent symptoms deserve evaluation and should not be dismissed as anxiety or something you must tolerate to keep your hair. Tell the clinician when symptoms began, how they changed with treatment and whether they remain after stopping. Do not restart or change the dose yourself after a concerning reaction.
Finasteride 1 mg can substantially lower PSA. In a randomized trial of men aged 40 to 60, median PSA fell by 40% to 50% after 48 weeks; the investigators recommended accounting for this reduction in screening as with the 5 mg preparation. Tell the clinician interpreting your PSA about current or past finasteride use. The clinician should interpret the result in context, including the dose, duration and prior values; a confirmed rise from the lowest PSA on treatment needs evaluation even if the result is within the usual reference range. Read the 1 mg PSA trial.
Trial sexual symptoms resolved after stopping in affected men and in most men who continued, but postmarketing reports include symptoms that persisted. A short drug half-life does not guarantee quick symptom recovery. Hair benefit generally reverses within 12 months of stopping; discuss any safety concern before deciding to continue for cosmetic benefit.
The label reports more high-grade prostate cancers in the prevention trial of finasteride 5 mg: 1.8% versus 1.1% with placebo. That study used five times the hair-loss dose in older men, so it is not an estimate of risk with 1 mg in younger men. It still belongs in the safety discussion; finasteride is not approved to prevent prostate cancer.
Finasteride must not be used during pregnancy. Someone who is or could be pregnant should not handle broken or crushed tablets; intact coated tablets prevent contact during normal handling. Wash exposed skin with soap and water and seek medical advice. Male infertility or poor semen quality has been reported, with improvement after stopping in some reports. Discuss fertility concerns rather than assuming a guaranteed recovery time. The American Red Cross requires waiting one month after the last finasteride dose before donating blood.
These sources support the medication facts and research discussed above. Study results apply to the doses and populations tested; they do not guarantee an individual outcome.
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