Dutasteride and finasteride are prescription medicines that lower dihydrotestosterone (DHT), a hormone made from testosterone. Clinicians use them, in licensed doses, for male pattern hair loss, benign prostate enlargement, or both—depending on the product, the country, and the person. This Health Insights page compares how they work, what patient information usually covers, and which questions to take to a licensed clinician. It does not choose a medicine or a dose for you.
How both medicines lower DHT
An enzyme called 5-alpha-reductase converts some testosterone into DHT. DHT can shrink hair follicles on the scalp in androgenetic alopecia, and it also contributes to growth of the prostate. Finasteride mainly blocks the type II form of that enzyme. Dutasteride blocks type I and type II. Because of that broader block, dutasteride usually lowers circulating DHT more than finasteride does at commonly prescribed doses. A larger drop in a lab number is not, by itself, proof that one medicine is safer or more suitable for you.
Both are taken by mouth, usually once a day, and both need time. Hair changes, when they occur, are often discussed over several months rather than days. Prostate symptom scores and urinary flow are judged on a similar slow timeline. Stopping the medicine generally lets DHT rise again, and hair or urinary benefits that depended on treatment can fade. Neither medicine is an emergency treatment for sudden chest pain, inability to pass urine, or a painful erection that will not settle—those need urgent care.
Hair loss and prostate uses are not the same license
Finasteride is widely licensed in two strengths that do different jobs. A lower daily strength is used for male pattern hair loss in men. A higher daily strength is used for benign prostatic hyperplasia (prostate enlargement). The NHS finasteride medicine page explains that hair-loss treatment can take three to six months to show an effect, that you keep taking it to maintain any benefit, and that it is not for women or children. MedlinePlus finasteride summarizes the same split: hair-loss use versus prostate use, plus safety warnings patients are asked to read before the first tablet.
Dutasteride 0.5 mg daily is widely licensed for benign prostate enlargement. Using it for hair loss is accepted in some practices and licensed in some countries, and it is off-label in others. “Off-label” means a clinician may still prescribe it when they judge the benefit worth the risk, but the official label you were handed may describe the prostate use only. Do not assume a hair-loss discussion on a website means dutasteride is approved for that purpose where you live.
These medicines are not interchangeable milligram for milligram. Finasteride 1 mg, finasteride 5 mg, and dutasteride 0.5 mg are different products. Switching, combining, or splitting tablets without a prescriber can change both the effect and the side-effect risk. Women who are pregnant or who could become pregnant should not take these medicines and should not handle crushed or broken tablets, because DHT-blocking drugs can harm the genital development of a male fetus.
Side effects worth naming before you start
Patient leaflets for both drugs describe sexual side effects in some men: lower libido, difficulty getting or keeping an erection, and changes in ejaculation. Breast tenderness, breast enlargement, and lumps should be reported. Mood change, including low mood and depression, is also listed; say so early if it appears. A small number of men report sexual symptoms that continue after they stop. That report does not prove how often it happens, and it is a reason to involve a clinician rather than to self-adjust the dose.
Both medicines lower prostate-specific antigen (PSA). A prostate blood test can look “better” than it is unless the clinician knows you take a 5-alpha-reductase inhibitor and interprets the result accordingly. Tell every new clinician, including surgeons and urology clinics, that you take finasteride or dutasteride. Liver disease, other hormone treatments, and plans for blood donation are also worth mentioning—some blood services defer donors who take dutasteride because the drug stays in the body for weeks. Ask the service that would collect the donation; do not rely on a forum rule.
Dutasteride’s longer stay in the body also means side effects, if they occur, may take longer to fade after the last dose than with finasteride. That is a practical difference, not a ranking. Age, other medicines, fertility plans, and whether the goal is hair, urine symptoms, or both should drive the choice.
Questions to bring to a clinician
- Is my goal hair loss, prostate symptoms, or both—and which product is licensed for that goal where I live?
- Which strength and schedule fit that goal, and how many months should we wait before judging the result?
- What sexual, breast, or mood symptoms should make me call you promptly?
- How should my PSA be read while I take this medicine?
- I may father a child or donate blood. Does that change the choice between finasteride and dutasteride?
Write the answers down, including the review date. US readers should treat this article as education and brand information only—not a pathway to purchase prescription medicine for the United States. In allowlist markets, catalog pages such as Finpecia 1 mg finasteride, Dutas 0.5 mg dutasteride, and the CHUMEDIC shop provide product context under local law and clinician oversight.
Sources
This content is not a substitute for professional medical advice—consult a licensed clinician.