Dutasteride is a capsule sometimes prescribed for male pattern hair loss in the UK. It is a prescription-only medicine, it is not licensed for hair loss, and it stays in the body for weeks, which affects side effects, stopping, blood tests and blood donation.

This guide covers who it is and is not for, the side effects and latest MHRA advice, and how prescribing works.

What dutasteride is, and why it is “off-label”

Dutasteride is a 5-alpha-reductase inhibitor, available in the UK as a 0.5 mg soft capsule, both as the brand Avodart and as generic dutasteride.

Its licensed use is an enlarged prostate. The Avodart summary of product characteristics (SmPC) lists it for the “treatment of moderate to severe symptoms of benign prostatic hyperplasia (BPH)”. A doctor prescribing it for male pattern hair loss is prescribing off-label, meaning outside the product licence. The SmPC says its effect on hair “was not formally studied during the phase III programme”.

MHRA guidance says that when prescribing off-label, prescribers should give patients “sufficient information about the proposed treatment, including known serious or common adverse reactions, to enable them to make an informed decision”.

Strength and regimen. Each capsule contains 0.5 mg of dutasteride. There is no licensed hair loss regimen, so your prescriber decides how you take it.

How it differs from finasteride

Both medicines lower dihydrotestosterone (DHT), a hormone involved in male pattern hair loss, by blocking 5-alpha-reductase, the enzyme that turns testosterone into DHT. That enzyme has two main forms:

  • Finasteride is “a competitive and specific inhibitor of type II 5α-reductase” (Propecia SmPC).
  • Dutasteride works by “inhibiting both type 1 and type 2, 5α-reductase isoenzymes” (Avodart SmPC).

Finasteride 1 mg (Propecia) is licensed in the UK for male pattern hair loss, and dutasteride is not. Finasteride’s half-life is about 5 to 6 hours in men aged 18 to 60, while dutasteride’s is measured in weeks.

None of this means one works better than the other for you. Which, if either, is appropriate is a decision for your doctor.

The long half-life, and what it means

A half-life is the time it takes for the amount of a medicine in your blood to fall by half. The Avodart SmPC says that with daily 0.5 mg dosing “the half-life is approx. 3-5 weeks”, so dutasteride takes months, not days, to leave your body. In practice:

  • side effects may not ease straight away after stopping
  • PSA blood test results “return to baseline within 6 months of discontinuing treatment”
  • you cannot give blood for 6 months after your last dose (see below)

Side effects

The Avodart patient leaflet lists these as common, affecting up to 1 in 10 men:

  • not being able to get or keep an erection
  • decreased sex drive (libido)
  • difficulty with ejaculation, such as less semen being released
  • breast enlargement or tenderness

For each sexual side effect, the leaflet says it “may continue after you stop taking Avodart”. The SmPC adds that “the role of dutasteride in this persistence is unknown”.

The leaflet also lists heart failure and changes in body hair as uncommon, and depression and testicular pain or swelling at an unknown frequency. These figures come from men treated for an enlarged prostate. It also warns that:

  • dutasteride can reduce sperm count, semen volume and sperm movement, so fertility may be reduced
  • you should tell your doctor about breast lumps or nipple discharge
  • you should stop and contact a doctor immediately if you have signs of an allergic reaction, such as a rash or swelling of the face or lips

Mood. The SmPC states that “mood alterations including depressed mood, depression and, less frequently, suicidal ideation have been reported in patients treated with another oral 5-alpha reductase inhibitor”.

The MHRA safety update of 11 May 2026

The MHRA’s Drug Safety Update of 11 May 2026 is mainly about finasteride, but covers dutasteride as a precaution. It said that “for dutasteride, a warning will be added to the SmPC and PIL that depressed mood, depression or suicidal ideation has been reported in patients receiving another medicine from the same class (finasteride)”, because “the data for dutasteride was very limited, therefore, PEAG and CHM recommended updating the dutasteride product information as a precaution”.

Its advice to patients includes:

  • “if you are prescribed finasteride 5mg or dutasteride and you develop depression or suicidal thoughts, contact your doctor as soon as possible”
  • “if prescribed finasteride or dutasteride and you experience decreased sex drive, difficulty having an erection or ejaculation problems you should contact your doctor for medical advice”
  • “if you have seriously harmed yourself or feel you are at risk of serious harm, contact emergency services on 999 immediately”

UK Yellow Card data from 1994 to 31 May 2025 included 5 reports of suicidal ideation and related terms for dutasteride 0.5 mg, and no fatal reports of suicide. A report does “not necessarily mean that the medicine has caused the reaction”.

If you need to talk to someone now, Samaritans are free on 116 123, day or night. Our MHRA safety updates page links to the original.

Who should not take it

From the Avodart SmPC and leaflet:

  • Women, children and adolescents. “This medicine is for men only. It must not be taken by women, children or adolescents.”
  • Allergies to dutasteride, other 5-alpha-reductase inhibitors, soya, peanut or any ingredient.
  • Severe liver disease. Tell your doctor about any liver problems.
  • Some other medicines, including verapamil, diltiazem, ritonavir, itraconazole and ketoconazole, can make side effects more likely. Tell your doctor everything you take.

Handling and pregnancy. The leaflet says: “Women who are pregnant (or may be) must not handle leaking capsules. Dutasteride is absorbed through the skin and can affect the normal development of a male baby.” Wash any skin contact immediately with soap and water. Dutasteride is also found in semen, so if your partner is or may be pregnant, use a condom.

Swallow capsules whole. “Do not chew or break open the capsule. Contact with the contents of the capsules may make your mouth or throat sore.”

Blood donation

The UK Blood Services’ donor guidelines (JPAC) say you must not donate if dutasteride has been “taken in the last 6 months”, because it “can cause abnormal development of the sexual organs of a male baby within the womb” and a donation could be given to a pregnant woman.

PSA tests

PSA (prostate-specific antigen) is a blood test sometimes used to help detect prostate cancer. The SmPC says dutasteride “causes a decrease in mean serum PSA levels by approximately 50%, after 6 months of treatment”. The test can still be used, but your doctor needs to know to read it correctly. The leaflet says: “If you are having a blood test for PSA, tell your doctor that you are taking Avodart.”

How prescribing works with a regulated UK service

The General Pharmaceutical Council (GPhC) explains that to obtain a prescription-only medicine online you “would need to have an appropriate consultation with a prescriber”. The medicine is then supplied by a registered pharmacy.

At WMG Meds, a service under Westminster Medical Group, 134 Harley Street, dutasteride may be considered where finasteride has not given an adequate response. The process is:

  1. A medical questionnaire covering your date of birth, liver and other conditions, any depression, low mood or self-harm, allergies, other medicines, and pregnancy and family planning, including a partner’s. Under-18s are not prescribed.
  2. Review by a GMC-registered doctor, who decides whether treatment is clinically appropriate. If it is not, the doctor tells you why.
  3. An explanation before any prescription: the off-label use, the MHRA advice, handling precautions and the trade-offs.
  4. Dispensing by our partner UK pharmacy, with delivery to UK addresses.
  5. Follow-up reviews, so the doctor can adjust or stop treatment.

The dutasteride 0.5 mg product page has the full product information, and the doctor-led assessment starts with the questionnaire.

What to expect over time

Hair grows slowly, so it takes months to judge any hair loss treatment. The first follow-up review is at around 3 months, with the plan reviewed against your response at around 6 months. Response varies between people.

Stopping dutasteride

Speak to your prescriber before stopping, unless you develop depression or suicidal thoughts, in which case contact your doctor as soon as possible. Because of the half-life, dutasteride takes weeks to months to clear. Mention it before any PSA test in the following 6 months, and remember the blood donation rule. Our guide to stopping dutasteride covers what to expect.

Red flags with unregulated sellers

The GPhC warns that “there are unregistered websites selling medicines that may not be genuine or haven’t been checked by a pharmacist”. Be wary if a seller:

  • offers dutasteride without a consultation or prescription
  • asks nothing about your health, mood, other medicines or a partner’s pregnancy
  • does not name the dispensing pharmacy, or it is not on the GPhC register
  • does not identify the prescriber, or the prescriber is not on the GMC register
  • offers no aftercare if you have side effects

Frequently asked questions

Can I buy dutasteride online in the UK without a prescription?

No. It is a prescription-only medicine. Online, you need an appropriate consultation with a prescriber, and it is then supplied by a registered pharmacy.

How much does dutasteride cost in the UK?

We do not publish prices for prescription-only medicines. If a doctor considers treatment appropriate, the price is confirmed after the clinical assessment. No card details are taken with the questionnaire.

What happens if I miss a capsule?

The Avodart leaflet says: “Do not take a double dose to make up for a forgotten dose. Just take your next dose at the usual time.”

Can women take dutasteride for hair loss?

No. The SmPC lists women, children and adolescents as contraindications.

How do I report a side effect?

Tell your prescriber. You can also report suspected side effects to the MHRA through the Yellow Card scheme.

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