What dutasteride is and which form this page covers
Dutasteride is a prescription medicine taken as a capsule. It is used for an enlarged prostate and, in some countries, male pattern hair loss. This guide is for adult men considering or already using the capsule for hair loss. It covers sexual symptoms, mood, fertility and what can happen after stopping. [1, 2, 3]
Approval depends on the country. In the US and UK, the checked capsule labels cover an enlarged prostate, so use for hair loss is off-label: a prescriber uses the medicine outside its authorised purpose. Japan has a separate hair-loss authorisation. The full dutasteride profile explains its benefits and how access differs. [1, 2, 3]
Sexual function
Mood
Fertility
These points come from hair-loss trials, product labels and regulatory warnings. The sections below explain how common symptoms were in the trials and where a reliable frequency is missing. Information about the capsule should be kept separate from the investigational scalp solution. [4, 5, 1, 6, 7]
How common are sexual side effects?
Most men in the two hair-loss trials discussed here did not report sexual symptoms. Some did, and the rate depended on how the study asked about them and what it counted. These are study-specific figures, not one fixed risk for everyone who takes dutasteride. [4, 5]
The large trial comparing dutasteride with finasteride randomised 917 men aged 20 to 50 across five treatment groups. It lasted 24 weeks, and 761 men completed it. GSK funded the trial. In the relevant groups, 184 men received dutasteride 0.5 mg daily, 179 received finasteride 1 mg daily and 181 received placebo, an inactive capsule. [4]
Researchers tracked sexual or breast-related events as a special category. At least one such event was recorded in 19 men taking dutasteride, 24 taking finasteride and 12 taking placebo. Because the category includes breast-related events, calling all of these reports sexual dysfunction would change what the study counted. [4]
Sexual or breast-related events over 24 weeks
Dutasteride 0.5 mg19 of 184 men
10.3%of men
Finasteride 1 mg24 of 179 men
13.4%of men
Placebo12 of 181 men
6.6%of men
Participants with at least one event in the trial's special sexual or breast-related category, not a lifetime risk. GSK funded this five-group trial. These counts do not establish that dutasteride is safer than finasteride, or that their safety is equal. [4]
Erection problems, described in the paper as impotence, were reported by 10 of 184 men on dutasteride, 11 of 179 on finasteride and 7 of 181 on placebo. These men are included in the broader category above. Adding those counts to the chart would count some participants twice. [4]
The lower dutasteride percentage does not show it is the safer choice. The trial was too limited to settle that comparison. The finasteride and dutasteride comparison also explains the hair-count result, which is a separate outcome from side effects.
Why do the percentages vary?
The percentages can vary with who takes part and how sexual symptoms are recorded. A smaller trial specifically investigated sexual function. It enrolled 117 sexually active men with male pattern hair loss. During the 24-week blinded comparison, at least one sexual event was reported by 9 of 58 men receiving dutasteride and 5 of 59 receiving placebo. These are roughly 16% and 8%. GSK funded the study, with company involvement among authors and editorial support. [5]
Those figures do not contradict the larger trial. This study asked directly about sexual function, involved a smaller sample and had reports concentrated in particular study centres. Its definition was also different from the combined sexual or breast-related category. It did not compare dutasteride with finasteride. [5]
Two studies, two ways of counting
| The larger comparison24 weeks | The sexual-function study24 blinded weeks | |
|---|---|---|
| What was counted | At least one sexual or breast-related event | At least one sexual event |
| Dutasteride | 19 of 184 men | 9 of 58 men |
| Placebo | 12 of 181 men | 5 of 59 men |
| Main limit here | Does not establish equal safety against finasteride | Small groups and study-centre differences |
Both were funded by GSK. Neither row supplies a universal percentage for every man who starts dutasteride. [4, 5]
A review combined 15 trials of finasteride or dutasteride, involving 4,495 participants overall. Its estimate for dutasteride 0.5 mg was too uncertain to pin down the size of any increase in sexual symptoms. The relative risk was 1.37, with a 95% confidence interval from 0.81 to 2.32: a range spanning slightly fewer events than placebo to more than twice as many. That uncertainty does not show there is no risk. The dutasteride subgroup also included a study in healthy volunteers. [8]
Comparing this pooled estimate with the review's separate finasteride estimate would not tell you which drug is safer. The review combines studies with different durations and reporting methods. For the tablet's own label figures and warnings, see finasteride side effects.
Can symptoms continue after stopping?
Yes, sexual symptoms can continue after stopping. The US Avodart label warns about this, while saying dutasteride's role in the persistence is unknown. We do not have a reliable percentage for how often it happens or a timetable for everyone's recovery. [1]
The small sexual-function trial offers some reassuring follow-up within a narrow scope. Events in dutasteride participants who were followed resolved. Four events still present at the end of treatment cleared within six weeks of the last dose. The study continued with an open treatment phase and targeted follow-up, but it could not exclude uncommon or later problems in the wider population. [5]
A practical record can make the discussion clearer: what changed, when it began, the exact product and schedule, and any other medicines in use. This is an organising suggestion, not a way of diagnosing the cause. The guide to tracking hair treatment covers records that include tolerability as well as photographs.
How long does dutasteride stay in the body?
Dutasteride leaves the body slowly: the US label says it can remain detectable for four to six months after stopping. Its half-life is about five weeks at steady state, when regular dosing has produced a stable drug level. Half-life is the time for that level to fall by roughly half. Finasteride's label describes a much shorter half-life, around five to six hours in men aged 18 to 60. [1, 9]
That difference matters to a conversation about starting or stopping. It does not measure how likely a side effect is, how long a symptom lasts, or when it is safe for an individual to try to conceive. Nor does it validate a self-designed schedule with fewer capsules. [1, 9]
- Dutasteride half-life
- About 5 weeksAt steady state in the US label.
- After the last dose
- 4 to 6 monthsDrug levels can remain detectable.
- Symptom duration
- Not predictedDrug clearance is not a recovery clock.
These figures describe how slowly oral dutasteride leaves the body. They do not set a personal waiting period or predict how long a symptom will last. [1]
The same caution applies to hair. We found no measurement of the hair outcome after stopping dutasteride in the sources reviewed. Medicine remaining in the bloodstream is not evidence that its visible benefit remains for the same period. The finasteride results guide describes a different medicine's maintenance evidence; its stopping timeline cannot be transferred here. [4, 10, 1]
Can dutasteride affect your mood?
The UK warns about possible mood changes with oral dutasteride, although the evidence for dutasteride itself is very limited. Its medicines regulator added the precautionary warning in May 2026, reflecting concern about the group of medicines it belongs to. The European review in 2025 likewise did not establish a causal link between dutasteride and suicidal thoughts. Neither conclusion is a guarantee of no risk. [6, 11]
For finasteride tablets, the regulatory conclusion is stronger: depression and suicidal thoughts are recognised concerns, and the European review confirmed suicidal thoughts as a side effect with unknown frequency. Stating that dutasteride has the same proven psychiatric risk would misrepresent those reviews. Treating its precaution as irrelevant would also misrepresent them. [6, 11]
The UK communication concerns oral products. It does not supply a measured psychiatric risk for a scalp solution. Topical dutasteride has its own limited study, which cannot settle uncommon mood or persistent adverse effects. [6, 7]
Can dutasteride affect fertility?
Dutasteride can change sperm count and other semen measures. Whether that changes an individual man’s fertility is unknown. The US label describes 27 healthy men who took dutasteride 0.5 mg and 23 who took placebo for 52 weeks. Average reductions, after accounting for the placebo group, were 23% in total sperm count, 26% in semen volume and 18% in sperm motility, the ability of sperm to move. The study measured semen rather than pregnancies or births. [1]
At 24 weeks after stopping, the mean total sperm count in the dutasteride group remained 23% below its starting value. Two men had reductions greater than 90% during treatment, with partial recovery during follow-up. A group average within a normal range does not exclude a large change for an individual. [1]
Mean reductions in semen measures at 52 weeks
Semen volume
26%reduction
Total sperm count
23%reduction
Sperm motility
18%reduction
Placebo-adjusted mean reductions in 27 healthy men taking dutasteride compared with 23 taking placebo. The study measured semen, not pregnancies or births. The label says the effect on individual fertility is unknown. [1]
These findings make existing fertility difficulties and plans for children relevant to the prescriber discussion. They do not justify a universal conception waiting period, a guarantee of recovery by a certain date, or a claim that dutasteride causes infertility in a specified proportion of users. [1]
What else should your prescriber know?
The US label warns that dutasteride can be absorbed through skin from a leaking capsule. The checked products are not indicated for women or children. Pregnancy and potential exposure are reasons to use the leaflet for the exact product and country, including its instructions about handling. The leaflet gives the handling instructions for that particular product. [1, 2]
Dutasteride also lowers PSA, a blood marker used in prostate assessment. In prostate trials, the reduction was about half within three to six months. The clinician interpreting a result needs to know about dutasteride use. These data do not create a universal test adjustment or screening schedule for men taking it for hair loss. [1]
Finasteride and dutasteride are alternatives from the same medicine group. The UK finasteride label excludes combining it with another medicine in that group. A trial comparing the drugs does not establish a switching or overlap schedule. The hair-loss routines guide separates tested combinations from duplication. [12, 4]
What should you discuss at a review?
A useful review connects three things: the benefit you hoped for, the changes you have actually noticed and the uncertainties you are willing to accept. Photos cannot assess sexual function, and a hair-count improvement does not cancel out a troublesome symptom. Conversely, a symptom appearing during treatment is something to assess, not a diagnosis of its cause.
Questions the evidence helps you frame
- What exact product and purpose does the prescription cover in my country?
- Which existing symptoms, medicines or fertility plans affect the decision?
- What should prompt contact before the planned review?
- How will benefit and tolerability be assessed separately?
- If a change is needed, what is the prescriber's plan rather than an improvised overlap?
For a wider choice, the hair treatment ranking explains why oral dutasteride is a conditional alternative. If the pattern itself is uncertain, the guide to hair-loss types is the more useful next read. A risk discussion only makes sense when the treatment is being considered for the right problem.
