Dutasteride (Avodart) for Hair Loss: What the Evidence Shows
Last reviewed on 12 July 2026. We review our treatment guides every six months to keep them accurate.
Dutasteride, sold under the brand name Avodart, is a prescription medicine that lowers the hormone dihydrotestosterone (DHT). In the UK it is licensed to treat an enlarged prostate, but it is also used, off-label, for male pattern hair loss, where it is one of the more potent options. This guide explains what dutasteride is, how it compares with finasteride, the results and timeline you can realistically expect, the safety points that matter most, including recent regulatory warnings, and the position for women. It is general information rather than medical advice, so please speak to a doctor or dermatologist about your own situation.
For the current UK safety position, the medicines regulator, the MHRA, publishes a drug safety update covering dutasteride and finasteride. It is the regulator's own page and is updated when the advice changes, so it stays current between our own reviews.
What dutasteride is and how it works
Dutasteride belongs to a group of medicines called 5-alpha-reductase inhibitors (5-ARIs). It works by blocking 5-alpha-reductase, the enzyme that converts testosterone into dihydrotestosterone (DHT). In men who are genetically susceptible, DHT binds to receptors in scalp hair follicles and gradually shrinks them, a process called miniaturisation, so the hairs they produce become finer and shorter until, in time, they may stop growing altogether. By lowering DHT, dutasteride is intended to slow that process and, in some men, allow a degree of regrowth where follicles are still active.
There are two forms of the 5-alpha-reductase enzyme, type 1 and type 2. What sets dutasteride apart is that it blocks both, whereas finasteride blocks mainly type 2. Because of this dual action, dutasteride lowers DHT more completely. The manufacturer's data show that a daily 0.5mg dose reduces DHT in the blood by around 85% within a week and about 90% within two weeks, reaching roughly 94% after a year. For comparison, finasteride is commonly reported to lower DHT by about 70%.
Dutasteride versus finasteride
The two medicines are closely related, and much of what is true of one is true of the other. The practical difference is that dutasteride is the more powerful DHT blocker of the two. In head-to-head trials it has increased hair count somewhat more than finasteride, which is covered in the next section. That extra potency comes with the same broad pattern of possible side effects rather than a milder one, so more DHT suppression is not automatically better for everyone. For most men, finasteride is the more commonly used first choice, and dutasteride tends to be considered by a specialist where finasteride has not done enough. Which, if either, is appropriate is a decision for a clinician.
Is dutasteride approved for hair loss?
This is an important point to be clear about. In the UK, dutasteride is licensed only to treat an enlarged prostate (benign prostatic hyperplasia), not hair loss. Using it for male pattern hair loss is therefore off-label, meaning a prescriber is using a licensed medicine outside the conditions it was approved for, after weighing up the alternatives. That is legal and not unusual, but it is worth knowing. Finasteride, by contrast, does hold a UK licence for male pattern hair loss at its 1mg dose.
In some other countries the position is different: dutasteride 0.5mg is separately approved for male pattern hair loss in South Korea, Japan and Taiwan, where much of the research on it has been carried out.
How well does it work, and how long does it take?
The evidence that dutasteride helps male pattern hair loss is reasonably consistent. In a 24-week phase III randomised trial of 576 men, and in a 2024 systematic review of the trials, dutasteride 0.5mg a day increased hair count more than finasteride 1mg, with a broadly similar rate of side effects. So on the specific measure of hair count, the studies tend to favour dutasteride.
It is only fair to add the caveats. The evidence base for dutasteride in hair loss is smaller and shorter-term than for finasteride, much of it comes from a small number of countries, and, as above, it is not licensed for hair loss in the UK. Like all these medicines, dutasteride can slow or partly reverse hair loss where follicles are still active, but it cannot bring back hair that has already been lost, and any benefit lasts only for as long as the medicine is taken.
Dutasteride results timeline
Results are gradual, and the timeline below is a realistic general guide rather than a promise. Individual outcomes vary, and some men see less change than others.
First few weeks: DHT in the blood falls quickly, within one to two weeks, but you will not see anything on the scalp yet. As with finasteride, some men notice a temporary increase in shedding early on as follicles reset their growth cycle. This is common and not a sign the medicine is failing.
Three to six months: the first signs of reduced shedding and, for some, early regrowth tend to appear in this window, often first around the crown. Trials usually take their first careful hair-count measurements at about this point.
Around twelve months: the fuller effect is usually clearer by about a year, with any improvement in density and thickness more established. This is generally when it is fair to judge how much the medicine is doing for you.
Because the benefit continues only while the medicine is taken, hair loss tends to resume if it is stopped, and ground gained can gradually be lost.
Side effects and safety
Many men take dutasteride without trouble, but it does carry real risks that are worth understanding. The best-recognised are sexual: reduced sex drive, difficulty getting or keeping an erection, and problems with ejaculation, including reduced semen volume. In the manufacturer's monotherapy trial data these were reported by a minority in the first year (for example, difficulty with erections in around 6%, reduced libido in about 3.7% and ejaculation problems in about 1.8%), and tended to become less common with continued use. Breast tenderness or enlargement can also occur and is uncommon.
Two points deserve particular attention. First, in a minority of men these sexual side effects can persist after the medicine is stopped; the product information notes this, while adding that dutasteride's role in that persistence is not established. Second, in May 2026 the UK medicines regulator, the MHRA, strengthened its warnings for both finasteride and dutasteride. Finasteride is associated with depression, suicidal thoughts and sexual dysfunction that may persist after treatment is stopped, and, because dutasteride works in the same way, a precautionary warning about depressed mood, depression and suicidal thoughts has been added to dutasteride's product information (its own reported data are very limited). Anyone taking dutasteride who develops low mood or thoughts of self-harm is advised to seek medical advice promptly. You can read the current position in the MHRA's drug safety update.
One practical difference from finasteride is that dutasteride stays in the body far longer, with a half-life of about three to five weeks (compared with a matter of hours for finasteride). It therefore clears very slowly, which is why some precautions, such as around blood donation, extend for months after the last dose.
Women and pregnancy
Dutasteride is contraindicated in women and is not licensed for female hair loss. The most important reason is pregnancy. Because DHT is needed for the normal development of a male baby, dutasteride, like other 5-alpha-reductase inhibitors, can interfere with that development, in particular the external genitalia. For this reason it must not be taken by anyone who is pregnant or who might become pregnant. As the drug is absorbed through the skin, anyone who could become pregnant should also avoid handling leaking capsules, and no one taking dutasteride should donate blood while on it or for six months after the last dose, so it cannot reach a pregnant recipient through a transfusion.
Dutasteride is sometimes discussed for women with hair loss, but only off-label, only under specialist supervision, and with weaker evidence than in men. If you are a woman considering treatment for hair loss, our guide to DHT blockers for women covers what the evidence actually shows and the safer starting points.
Dutasteride and PSA blood tests
Dutasteride lowers PSA (prostate-specific antigen), the blood marker used in prostate-cancer screening. That matters because a lowered PSA reading could mask a result that would otherwise prompt further checks. If you take dutasteride, tell any doctor who arranges a PSA test, so the result can be interpreted correctly; in prostate treatment a new PSA baseline is usually set after about six months on the medicine.
Other options
Dutasteride is not the only route. Finasteride is the more commonly used first-line 5-alpha-reductase inhibitor and is licensed for hair loss in the UK. Minoxidil works in a different way, as a topical hair-growth stimulant rather than a DHT blocker, and is often used alongside or instead of these medicines. Which of these fits your situation, and whether dutasteride is a sensible option for you at all, is best worked through with a GP or dermatologist who can weigh the benefits and the risks for you.
Frequently asked questions
Frequently asked questions
How long does dutasteride take to work?
Results are gradual. DHT in the blood falls within one to two weeks, but visible change takes months. Some men shed a little more hair early on, then see the first signs of reduced shedding and early regrowth over roughly three to six months, with the fuller effect usually clearer by about a year. It only works while it is taken, so any benefit is lost if the medicine is stopped. Individual results vary.
Is dutasteride better than finasteride?
On hair count, the trials tend to favour dutasteride: it blocks DHT more completely and, in head-to-head studies, increased hair count somewhat more than finasteride, with a similar rate of side effects. But the evidence base for dutasteride in hair loss is smaller and shorter-term, and it is not licensed for hair loss in the UK, whereas finasteride is. For most men finasteride is the usual first choice, with dutasteride considered by a specialist if finasteride has not done enough. There is no single right answer for everyone.
Can women take dutasteride for hair loss?
Dutasteride is contraindicated in women and is not licensed for female hair loss. It must not be taken by anyone who is pregnant or who could become pregnant, because it can affect the development of a male baby, and leaking capsules should not be handled for the same reason. It is occasionally used off-label under specialist supervision, but with weaker evidence than in men. Our DHT blockers for women guide explains the safer starting points.
Is dutasteride (Avodart) safe?
Many men tolerate it well, but it is not risk-free. The main side effects are sexual (reduced sex drive, erectile and ejaculation problems), which in a minority can persist after stopping. In May 2026 the MHRA strengthened warnings for both finasteride and dutasteride around depression, suicidal thoughts and sexual dysfunction that may persist. Dutasteride also lowers PSA, which matters for prostate-cancer screening. Whether it is a safe choice for you depends on your own health and history, which is a conversation to have with a clinician.
Is dutasteride approved for hair loss in the UK?
No. In the UK dutasteride is licensed only for an enlarged prostate, so any use for hair loss is off-label. It is separately approved for male pattern hair loss at 0.5mg in South Korea, Japan and Taiwan. Finasteride, by contrast, is licensed for male pattern hair loss in the UK.
The bottom line
Dutasteride, or Avodart, is the more potent of the two main DHT-blocking medicines, and in trials it has edged ahead of finasteride on hair count. Against that, it is not licensed for hair loss in the UK, its evidence base is smaller, and it carries the same sexual and mood-related risks as finasteride, now covered by strengthened MHRA warnings, along with a long stay in the body and effects on PSA testing. It is contraindicated in women and must be avoided in pregnancy. None of this is a substitute for individual advice, so if you are weighing up dutasteride for hair loss, talk it through with a GP or dermatologist who can look at your own situation.
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