Dutasteride 0.5mg is licensed in the UK for benign prostatic hyperplasia — an enlarged prostate. It is not licensed here for androgenetic alopecia. When a UK prescriber supplies it for hair loss, they are prescribing off-label.
Off-label prescribing is legal, common and often entirely appropriate. But it shifts responsibility onto the prescriber, and it means the manufacturer's information leaflet will not describe the use you are putting it to. You should be told this explicitly before you start. If a service supplies dutasteride for hair loss without mentioning it, that is a gap in the consultation.
How It Differs From Finasteride
Both are 5-alpha reductase inhibitors: they reduce conversion of testosterone into DHT, the hormone that miniaturises follicles in genetically susceptible people.
- Finasteride inhibits the type II isoenzyme.
- Dutasteride inhibits both type I and type II.
Broader inhibition produces a greater reduction in circulating DHT, which is why dutasteride is sometimes tried when finasteride has not delivered. It also has a considerably longer half-life, so it clears from the body much more slowly — relevant if you need to stop, and relevant to anyone planning to donate blood or conceive.
Effectiveness
Trials comparing the two generally favour dutasteride on hair count and thickness measures. The difference is real but not transformative, and it comes with a correspondingly broader hormonal effect. The sensible framing is that dutasteride is a step up in intensity rather than a different kind of treatment.
Side Effects and the 2026 Safety Update
In May 2026 the MHRA strengthened product information for both finasteride 1mg and dutasteride 0.5mg on psychiatric and sexual side effects. For dutasteride specifically, a precautionary warning was added noting that mood alterations have been reported with related medicines.
The recognised effects to know about:
- Reduced libido
- Erectile dysfunction
- Ejaculation disorders
- Breast tenderness or enlargement
- Mood changes, including depression
Most are uncommon. But the MHRA's position is that sexual dysfunction may persist after stopping, and that sexual dysfunction can itself contribute to low mood. Anyone who develops depression or suicidal thoughts should stop and seek medical advice promptly.
Who Should Not Take It
Dutasteride is not for women, and is specifically hazardous in pregnancy — it can affect the development of a male foetus. Capsules should not be handled by women who are or may become pregnant, particularly if leaking. Men taking it should not donate blood until at least six months after stopping, because of the risk to a pregnant recipient.
It also lowers PSA readings, which matters for prostate cancer screening. Tell any doctor interpreting a PSA test that you take it.
Cost in the UK
Because it is off-label for hair loss, dutasteride is not something you will get on the NHS for this purpose. Prices vary considerably between online providers, and the generic is substantially cheaper than the branded version (Avodart). As with all of these, the number worth comparing is the ongoing monthly cost — this is treatment you continue indefinitely, so a small monthly difference compounds over years.
Is It Worth Considering?
The usual sequence is finasteride first, with dutasteride considered if response is inadequate after a fair trial — and a fair trial means at least six to twelve months, not six weeks. Going straight to the broader inhibitor without establishing whether the narrower one works is accepting more hormonal effect than you may need.