Treatment tracking
Dutasteride vs finasteride for hair loss: what the evidence says, and how to know if switching helped
Dutasteride lowers DHT more than finasteride because it blocks both forms of the enzyme that makes it, not just one. In a 24-week trial of 917 men, dutasteride 0.5 mg increased hair count and hair width more than finasteride 1 mg. It’s approved for hair loss in some countries, but in the US it’s prescribed off-label, and it stays in the body much longer than finasteride, so any side effects can take longer to fade.
How they differ
Both drugs block 5-alpha reductase, the enzyme that turns testosterone into DHT, the hormone behind pattern hair loss. Finasteride blocks one form of the enzyme (type II). Dutasteride blocks both type I and type II, so it lowers DHT further.
| Finasteride 1 mg | Dutasteride 0.5 mg | |
|---|---|---|
| Enzyme blocked | Type II | Types I and II |
| Approved for hair loss | Yes (US and widely) | In some countries; off-label in the US |
| Time in the body | Short; cleared in days | Long; weeks to months |
| Blood donation | Short wait after the last dose | A much longer wait (blood services commonly ask for about 6 months) |
What the trial found
Gubelin Harcha and colleagues randomized 917 men aged 25–50 to several doses of dutasteride, finasteride 1 mg, or placebo for 24 weeks. Dutasteride 0.5 mg was statistically superior to both finasteride 1 mg and placebo at increasing hair count and hair width.1 Finasteride’s own long-term data are covered in the finasteride timeline.2
24 weeks is short for hair, so the trial shows dutasteride works faster or harder over six months, not what happens after five years.
Trade-offs
- Stronger DHT suppression tends to mean somewhat better results, with the same kind of possible side effects as finasteride, mainly sexual ones. Ask your doctor about everything on its label.
- Long half-life. If side effects appear, they can take much longer to fade after stopping than with finasteride.
- Off-label in the US. It’s a prescribing decision for a doctor who knows your history.
- Not for women who are or may become pregnant, and they shouldn’t handle leaking capsules.
How to know if switching helped
Men usually switch because finasteride seems to have stalled. The switch is only worth its trade-offs if it measurably helps, and averages from a trial don’t tell you that about yourself.
- Measure while still on finasteride to set the baseline.
- Switch only the drug, nothing else that month.
- Rescan the same spots every 2 months for at least 6 months.
- Look at hair thickness on top against the back of your head. If the ratio climbs faster than it did on finasteride, the switch is earning its place.
Measure the switch instead of guessing
GraftReport measures hair thickness zone by zone against your own control area, so you can compare your trend on finasteride with your trend after switching.
Get the kit — $199How treatment tracking worksCommon questions
Is dutasteride better than finasteride for hair loss?
In a 24-week trial of 917 men, dutasteride 0.5 mg increased hair count and hair width more than finasteride 1 mg. It also lowers DHT more and stays in the body much longer, which matters if side effects occur.
Is dutasteride approved for hair loss?
It is approved for hair loss in some countries. In the US it is prescribed off-label for hair loss, so the decision rests with a doctor.
How long does dutasteride stay in your system?
Much longer than finasteride: weeks to months rather than days. Blood services commonly ask donors to wait about six months after the last dose.
Should I switch from finasteride to dutasteride?
That is a decision for your doctor. If you switch, measure before and every couple of months after for at least six months, so you know whether it made a difference for you.
Sources
- Gubelin Harcha W et al. A randomized, active- and placebo-controlled study of the efficacy and safety of different doses of dutasteride versus placebo and finasteride in the treatment of male subjects with androgenetic alopecia. J Am Acad Dermatol. 2014;70(3):489–498. abstract
- Kaufman KD et al. Finasteride in the treatment of men with androgenetic alopecia. J Am Acad Dermatol. 1998;39(4):578–589. abstract
This guide is general information, not medical advice. Hair loss has many causes; see a dermatologist for sudden, patchy or painful hair loss, or before starting or stopping any medication.