Dutasteride vs finasteride for hair loss: What is the difference?
- How the two medicines differ in mechanism and DHT reduction
- What the comparative clinical evidence shows
- How their side effect profiles compare
- UK availability, dosing, and cost
- Who might be prescribed dutasteride instead of finasteride
- How do dutasteride and finasteride work differently?
- Which is more effective for hair loss?
- How do the side effect profiles compare?
- Full comparison table
- Who might be prescribed dutasteride instead of finasteride?
- What should you consider when switching from finasteride to dutasteride?
- How do costs compare in the UK?
- Final thoughts
How do dutasteride and finasteride work differently?
Finasteride inhibits only type II 5-alpha reductase, reducing serum DHT by approximately 60-70%. Dutasteride inhibits both type I and type II, reducing serum DHT by approximately 90-95%. This dual inhibition produces stronger DHT suppression and, in clinical trials, greater hair retention and regrowth.
Which is more effective for hair loss?
Clinical trials that have tested dutasteride and finasteride directly against each other consistently favour dutasteride. One study compared dutasteride 0.5 mg against finasteride 1 mg in 917 men over 24 weeks, finding significantly greater improvements in hair count and patient-assessed outcomes with dutasteride. A separate study similarly found dutasteride outperformed finasteride at 12 and 24 weeks.
The evidence consistently favours dutasteride for efficacy. However, its off-label status in the UK means the prescribing decision involves more than efficacy alone.
How do the side effect profiles compare?
Both medicines carry similar classes of side effects, reflecting their shared mechanism. The most clinically important difference is how long side effects last, rather than how often they occur.
| Side effect | Finasteride 1 mg | Dutasteride 0.5 mg |
|---|---|---|
| Decreased libido | Approx. 1–2% | Slightly higher reported incidence |
| Erectile dysfunction | Approx. 1–2% | Slightly higher reported incidence |
| Depression/mood changes | Uncommon (MHRA label) | Uncommon |
| Side effect persistence after stopping | Weeks | Weeks to months |
Sources: Finasteride 1 mg and Dutasteride Summaries of Product Characteristics, medicines.org.uk.
Dutasteride has a half-life of approximately five weeks, compared to five to six hours for finasteride. If side effects occur and treatment is stopped, dutasteride takes considerably longer to clear the body. Side effects may therefore persist for weeks or months after stopping, rather than days or weeks with finasteride. This is one of the most important practical distinctions between the two medicines and should be discussed with your prescriber before starting dutasteride.
Warning !
If you experience sexual side effects, low mood, or any thoughts of self-harm while taking either medicine, stop treatment and contact your GP promptly.
Full comparison table
| Finasteride | Dutasteride | |
|---|---|---|
| Mechanism | Type II 5-alpha reductase inhibitor | Dual type I and II inhibitor |
| DHT reduction | Approx. 60–70% | Approx. 90–95% |
| Licensed for hair loss in UK | Yes (1 mg) | No (off-label) |
| Standard dose for hair loss | 1 mg daily | 0.5 mg daily (off-label) |
| Half-life | Approx. 5–6 hours | Approx. 5 weeks |
| Comparative efficacy | Well-established | Superior in head-to-head trials |
| Side effect persistence after stopping | Weeks | Weeks to months |
| Typical private monthly cost | From approx. £15–£30 | From approx. £20–£40 |
Prices are indicative. Always confirm current pricing with your GPhC-registered provider.
Who might be prescribed dutasteride instead of finasteride?
Dutasteride may be considered for men who have used finasteride for twelve months or more without sufficient benefit, or where a prescriber determines that greater DHT suppression is clinically appropriate based on the patient's response history.
It is not a routine first-line option. For most men, finasteride remains the appropriate starting point as the licensed treatment with the most established evidence base.
Good to know
Your prescriber must clearly explain and document the off-label status of dutasteride for hair loss before prescribing. Patients should be explicitly informed before starting treatment.
What should you consider when switching from finasteride to dutasteride?
- Side effects experienced on finasteride may recur on dutasteride and may persist for longer due to the longer half-life
- No formal washout period is required between the two medicines, but your prescriber may advise a gap based on your individual history
- Greater DHT suppression does not guarantee proportionally greater results in every individual
How do costs compare in the UK?
Neither medicine is available on the NHS for hair loss. Both require a private prescription. Generic finasteride typically costs from approximately £15 to £30 per month privately; generic dutasteride from approximately £20 to £40 per month. Always confirm current pricing with your GPhC-registered provider before ordering.
Final thoughts
Dutasteride produces greater DHT suppression and superior outcomes in head-to-head clinical trials compared to finasteride. For men who have not achieved sufficient results with finasteride, it represents a clinically credible next step. Its off-label status in the UK, and the implications of its long half-life for side effect persistence, mean the decision to use or switch to dutasteride requires careful clinical discussion rather than a straightforward substitution.
DoktorABC connects UK patients with licensed prescribers who can assess suitability for finasteride or dutasteride and issue private prescriptions where clinically appropriate.
FAQ
What is the difference between dutasteride and finasteride?
Finasteride inhibits type II 5-alpha reductase only; dutasteride inhibits both type I and II, producing approximately 90 to 95% DHT reduction versus 60 to 70% with finasteride.
Is dutasteride more effective than finasteride for hair loss?
Head-to-head trials show greater hair count improvements with dutasteride. However, it is not licensed for hair loss in the UK and its use is off-label.
Does dutasteride have worse side effects than finasteride?
Side effect classes are similar. The most meaningful difference is that dutasteride's much longer half-life means effects may persist for longer after stopping.
Is dutasteride licensed for hair loss in the UK?
No. Its use for hair loss is off-label. This must be clearly disclosed by your prescriber before treatment begins.
Can I switch from finasteride to dutasteride?
Yes, under prescriber guidance. Side effect history, off-label status, and the longer half-life should all be discussed before switching.
Where can I report a side effect from dutasteride or finasteride?
Via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk, through the Yellow Card app, or by asking your prescriber or pharmacist to report on your behalf.
The DoktorABC medical advisory board
Dr. Roland Ruiken
Medical advisor, Norway
Dr. Viktor Simunovic
Medical advisor, Croatia