Dutasteride is a dual 5-alpha-reductase inhibitor (types I and II), reducing serum DHT by up to 90–95% — significantly more than finasteride's 60–70%. While not FDA-approved for hair loss in the US (it is in South Korea and Japan), it is widely prescribed off-label by hair loss specialists for cases where finasteride has plateaued.
Unlike finasteride which only inhibits 5α-reductase type II, dutasteride blocks both type I and type II isoenzymes. Type I activity accounts for a meaningful portion of scalp DHT production, so dual inhibition produces near-complete DHT suppression — making dutasteride significantly more potent.
Decreased libido
CommonEjaculatory dysfunction
CommonErectile dysfunction
UncommonGynecomastia (breast tissue growth)
UncommonSemen volume reduction
CommonMood changes
UncommonProlonged sexual side effects after stopping (longer half-life than finasteride)
UncommonDutasteride has a much longer half-life (5 weeks) than finasteride; side effects persist longer after stopping.
Blood donation is prohibited for 6 months after stopping due to risks to recipients.
Not safe for women of childbearing potential.
PSA suppression is greater than finasteride — baseline test recommended.
Typical Dose
0.5mg once daily (or 0.5mg 3x/week per some protocols)
Onset Time
6–12 months, with continued improvement to 36 months
Category
oral
Using minoxidil + microneedling?
Calculate your exact safe re-application window.
Open Lockout CalculatorTrack Dutasteride with protocol.hair
Daily reminders, streak tracking, inventory alerts, and automated lockout timers — all in one place.
Start free trialMedical disclaimer: The information on this page is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider or dermatologist before starting, stopping, or modifying any medication or treatment protocol. Hair loss medication interactions and individual responses vary significantly.