5-alpha reductase inhibitorPrescription only
Finasteride
Tablet
Quick Summary
Finasteride lowers DHT, a hormone that makes the prostate grow.
Enlarged prostate
Male pattern hair loss
Medical Uses
Enlarged prostate: Long-term.
Male pattern hair loss: Lower-strength form.
How it's taken
Take once a day; it takes months to work.
Your doctor decides the right dose for you and how long to take it.
Your doctor decides the right dose for you. Follow their instructions and the label.
Common Side Effects
Sexual side effects
Lower sex drive.
Breast tenderness
Sometimes.
Mood changes
Rarely.
Interactions
PSA tests
Finasteride lowers PSA results; tell your doctor.
Critical Warnings
Pregnancy
Black Box Warning: Women who are or may become pregnant shouldn't handle broken tablets.
Mood changes
Report low mood.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Finasteride: drug information(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Finasteride: a medicine for benign prostate enlargement and hair loss(opens in a new tab) · NHS