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What are DHT blockers for hair loss?
Short answer
"DHT blocker" is a popular name for a 5-alpha-reductase inhibitor, a medicine that lowers dihydrotestosterone (DHT), the hormone linked to pattern hair loss. In the UK, finasteride 1 mg is the licensed one for male pattern hair loss. Dutasteride is licensed for an enlarged prostate and used off-label for hair loss. Supplements sold as DHT blockers are not licensed medicines. Both medicines carry MHRA warnings.
Key facts
- Finasteride inhibits type II 5-alpha-reductase. Finasteride 1 mg is licensed in the UK for men with male pattern hair loss.
- Dutasteride inhibits type 1 and type 2 5-alpha-reductase. It is licensed in the UK for an enlarged prostate; hair loss use is off-label.
- Both are prescription-only, for men only in this context, and carry MHRA warnings on mood and on sexual side effects that may persist.
- No supplement, shampoo or oil is licensed in the UK as a DHT blocker for hair loss.
- Minoxidil is not a DHT blocker. It acts differently.
What DHT does to hair
Dihydrotestosterone (DHT) is made from testosterone by enzymes called 5-alpha-reductases. In male pattern hair loss, scalp follicles are sensitive to it. The Propecia summary of product characteristics (SmPC) says the balding scalp has miniaturised follicles and higher DHT levels, and that men born without type II 5-alpha-reductase do not develop male pattern hair loss. Our entries on DHT and 5-alpha-reductase explain the biology, and androgenetic alopecia covers the condition.
A "DHT blocker" is any treatment claimed to cut DHT. Medically, the ones with a regulatory standing are 5-alpha-reductase inhibitors.
The medicines
Finasteride. The SmPC describes it as a competitive and specific inhibitor of type II 5-alpha-reductase. The 1 mg tablet is licensed for men with male pattern hair loss; the 5 mg tablet is licensed for an enlarged prostate. See how to take finasteride.
Dutasteride. The Avodart SmPC describes it as inhibiting both type 1 and type 2 isoenzymes. It is licensed in the UK for an enlarged prostate, so its use for hair loss is off-label. See is dutasteride licensed for hair loss.
Topical finasteride. Not licensed in the UK; an unlicensed special if prescribed. See what is topical finasteride.
We do not rank these by how much DHT they lower. The figures come from different trials in different groups of men, and the amount of DHT lowered does not tell you how your own hair will respond or what side effects you may have. A doctor decides what, if anything, is appropriate for you.
Safety: the MHRA warnings
The MHRA issued Drug Safety Updates on 29 April 2024 and 11 May 2026. Finasteride is associated with low mood, depression, suicidal thoughts and sexual dysfunction that may persist after stopping, and if you develop depression or suicidal thoughts on finasteride 1 mg you should stop it and contact your doctor straight away. As a precaution, the 2026 update added a mood warning to the dutasteride product information too, because it works in the same way, noting that the data for dutasteride are very limited. Read our guides to finasteride side effects and dutasteride side effects.
If you are struggling with your mood, call Samaritans free on 116 123, call NHS 111, or call 999 or go to A&E if you feel at serious risk. Report suspected side effects through the Yellow Card scheme.
Other points shared by the class: both lower the PSA blood test, affect blood donation (4 weeks for finasteride, 6 months for dutasteride), and are not for women, with handling precautions for anyone who is or may be pregnant.
Supplements and "natural DHT blockers"
Products sold as natural DHT blockers include saw palmetto, pumpkin seed oil and various plant extracts. These are food supplements or cosmetics, not licensed medicines, and the evidence for them in hair loss is far more limited. Our guides to natural DHT blockers and saw palmetto set out what the studies show. Ketoconazole shampoo is sometimes described the same way; see ketoconazole shampoo for hair loss.
Other ways to treat hair loss
Minoxidil is a different kind of treatment and does not work by blocking DHT. Not everyone wants or should take a DHT-blocking medicine, and choosing no medicine is a valid decision. A GMC-registered doctor can talk through the options in the free online assessment; see also how treatments work and male pattern hair loss.
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Start your free assessment →Related questions
What is a DHT blocker?
A medicine or product claimed to lower dihydrotestosterone (DHT). The medicines with a regulatory standing are 5-alpha-reductase inhibitors, finasteride and dutasteride.
Is finasteride a DHT blocker?
Yes. The Propecia SmPC describes it as an inhibitor of type II 5-alpha-reductase, the enzyme that converts testosterone to DHT. The 1 mg tablet is licensed for male pattern hair loss.
Is minoxidil a DHT blocker?
No. Minoxidil works differently and does not act on 5-alpha-reductase.
Are DHT blockers available over the counter in the UK?
Finasteride and dutasteride are prescription-only. Supplements sold as DHT blockers are not licensed medicines.
Do DHT blockers have side effects?
Yes. The MHRA warns about low mood, depression, suicidal thoughts and sexual dysfunction that may persist after stopping. Read the patient leaflet and card, and contact your doctor about any change.
Sources
- Propecia 1 mg: summary of product characteristics (eMC, revised 29 June 2026)
- Avodart 0.5 mg soft capsules: summary of product characteristics (eMC, revised 11 August 2026)
- Proscar 5 mg: summary of product characteristics (eMC, revised 20 December 2024)
- MHRA Drug Safety Update, 11 May 2026: Finasteride and dutasteride, updated safety warnings
- MHRA Drug Safety Update, 29 April 2024: Finasteride, reminder of the risk of psychiatric side effects and of sexual side effects
- JPAC, Guidelines for the UK Blood Transfusion Services: Anti-androgens (whole blood, 17 September 2026)
Facts checked against these sources on 22 October 2026. This page is general information, not personal medical advice. Read our editorial policy.