Dutasteride vs Finasteride for Hair Loss

Dutasteride blocks more DHT than finasteride and usually comes out ahead in clinical trials. But how much extra hair does that actually produce? Many communities online now suggest people start immediately on dutasteride and skip finasteride, but is dutasteride the better choice for everyone, and should we skip finasteride?

The evidence says yes. A 24-week randomised trial involving 917 men found that dutasteride 0.5mg produced greater increases in hair count and hair width than finasteride 1mg. A later meta-analysis combined three randomised trials involving 576 men and again favoured dutasteride across hair count, before-and-after photographs assessed by researchers and the men’s own ratings of their results.

However, "better on average" is not the same as "better for every man". These studies compared average results between groups over a relatively short period. They cannot tell you whether the difference will be obvious when you look in the mirror, whether finasteride is already providing enough DHT suppression for you or which medicine you will be able to take every day for years without suffering any side effects.

Dutasteride is the more potent DHT blocker and you could consider using it when finasteride has not controlled ongoing hair loss and you are still losing hairs. It does not automatically mean you should swap from finasteride to dutasteride when finasteride is already keeping your hair where it is.

Finasteride and dutasteride both reduce DHT by inhibiting 5-alpha-reductase, the enzyme that converts testosterone into DHT. Finasteride mainly inhibits type II 5-alpha-reductase, while dutasteride inhibits both type I and type II. This allows dutasteride to suppress DHT more completely.

In a 42-day study involving 249 men with male pattern hair loss, finasteride 1mg reduced serum DHT by approximately 71% and DHT within scalp skin by approximately 64%. Dutasteride 0.5mg has reduced serum DHT by around 90% after two weeks and 94% after one year, although those longer-term figures come from men taking it for an enlarged prostate rather than hair loss. ^[2][5]

This seems massive and people see this on a graph and think "wow what's the point in bothering with finasteride". A 20-percentage-point difference in DHT suppression does not mean dutasteride will produce 20% more hair. It also does not mean finasteride only prevents 70% of somebody’s hair loss. How a person’s hair responds depends on factors including how sensitive their follicles are to DHT, how far those follicles have already miniaturised and whether finasteride has already reduced DHT sufficiently to stop further progression.

The dose studies of finasteride show why these percentages should not be treated as a simple scale of effectiveness. In the same study, finasteride 0.2mg reduced serum DHT by 68.6%, finasteride 1mg reduced it by 71.4% and finasteride 5mg reduced it by 72.2%. Increasing the dose from 1mg to 5mg therefore produced very little additional DHT suppression, and the prescribing information for finasteride states that there is no evidence that increasing the dose improves its effectiveness for hair loss. ^[1][5]

Dutasteride’s additional DHT suppression is still meaningful, and the head-to-head trials suggest that it can translate into greater average hair growth but we cannot calculate how much better it will be simply by comparing 70% with 90%.

The largest direct comparison involved 917 men aged between 20 and 50. They were randomly assigned to take dutasteride 0.02mg, 0.1mg or 0.5mg, finasteride 1mg, or a placebo for 24 weeks.

Rather than relying only on before-and-after photographs, the researchers marked a circular area of scalp and counted the hairs growing within it. They also measured hair width and had the photographs assessed by investigators and an independent panel.

Dutasteride 0.5mg produced a significantly greater increase in hair count and hair width than finasteride 1mg. The independent assessment of frontal scalp photographs also favoured dutasteride. However, the study lasted for only 24 weeks, so it tells us more about the difference after six months than it does about taking either medicine for several years. ^[3]

A 2019 meta-analysis then combined three randomised trials involving 576 men. After 24 weeks, the average improvement in total hair count was 28.57 hairs greater with dutasteride than with finasteride. The photographs assessed by researchers and independent panels also favoured dutasteride, as did the men’s own ratings of their results. ^[4]

This does not mean dutasteride adds another 29 hairs per cm². It was the pooled difference between the average changes in the treatment groups within the scalp areas measured by the studies. In the largest trial, the main target area was a circle 2.54cm in diameter, covering just over 5cm² of scalp. The pooled figure came from several trials, however, so it should not be divided by that area and converted into a universal hair-density gain.

It also does not mean every man taking dutasteride will grow exactly 29 more hairs than he would have grown on finasteride. Some men will see a greater difference, some a smaller one and some may see no obvious difference at all. It is a comparison between the average results of two groups, not a prediction for an individual person.

A much smaller randomised trial published in 2026 compared finasteride 1mg with dutasteride 0.5mg in 46 men with moderate-to-severe male pattern hair loss. Hair density and thickness improved in both groups over 24 weeks, but the researchers did not find a statistically significant difference between the treatments. The men’s satisfaction scores were also similar. ^[6]

This study was small with 23 men in each treatment group, and may have been too small to reliably detect anything other than a large difference. It does, however, reinforce the point that stronger DHT suppression does not guarantee a noticeably better result in every group of men.

Taken together, the available evidence still leans towards dutasteride producing greater hair growth on average. What it cannot tell us is whether the additional improvement will be visible on your own scalp, whether it will continue to widen after six months or whether finasteride would already have been enough to prevent your hair loss from progressing.

You might expect because dutasteride suppresses more DHT than finasteride that it will also cause more side effects, but the trials do not directly show this.

Both medicines have similar side effects and can cause sexual side effects, including a reduced sex drive, difficulty getting or maintaining an erection and ejaculation problems. In the 2019 meta-analysis of three head-to-head trials, there was no statistically significant difference between dutasteride and finasteride in the rates of altered libido, erectile dysfunction or ejaculation disorders after 24 weeks. ^[4]

Sexual side effects were relatively uncommon within the trials, and the studies were too small and too short to reliably detect modest differences, uncommon reactions or symptoms that continued after treatment had ended.

The figures quoted for these medicines often appear inconsistent because they come from different studies that asked about side effects in different ways.

In the clinical trials included in the prescribing information for finasteride 1mg, drug-related sexual side effects were reported by 3.8% of men taking finasteride and 2.1% taking a placebo during the first year. More specifically:

1. Reduced libido was reported by 1.8% taking finasteride and 1.3% taking placebo.
2. Erectile dysfunction was reported by 1.3% and 0.7%.
3. Reduced ejaculate volume was reported by 0.8% and 0.4%.

Around 1% of men in each group stopped treatment because of a sexual side effect. The incidence also declined with continued treatment. ^[1]

A separate study involving 117 men was designed specifically to monitor sexual function during dutasteride treatment. During its first 24 weeks, sexual side effects were reported by 16% of men taking dutasteride 0.5mg and 8% taking a placebo. The events were mild to moderate and resolved either while treatment continued or after it had ended. ^[7]

The studies involved different groups of men and used different methods so we cannot directly say that dutasteride is four times as likely to cause side effects than finasteride. A trial set up specifically to question and monitor men about their sexual function is likely to identify more symptoms in both the treatment and placebo groups than a general hair-loss trial.

The fairest conclusion is therefore that both medicines can cause sexual side effects, but the available data cannot establish that dutasteride causes significantly more of them.

Most sexual side effects recorded during controlled trials resolved either while treatment continued or after the medicine was stopped, however the UK prescribing information for finasteride includes reports of reduced libido, erectile dysfunction and ejaculation disorders continuing after treatment was discontinued. The dutasteride prescribing information also states that sexual side effects may persist after stopping, although it says dutasteride’s role in that persistence is unknown. ^[1][2]

In May 2026, the MHRA strengthened its safety advice for both medicines. It states that finasteride has been associated with depression, suicidal thoughts and sexual dysfunction that may persist after treatment is stopped. Men taking finasteride 1mg should stop treatment and contact a healthcare professional if they develop depression or suicidal thoughts.

The psychiatric warning for dutasteride is more of a precaution. The MHRA found that direct data for dutasteride were very limited, but recommended adding a warning because it works in a similar way to finasteride. Men taking dutasteride should contact their healthcare professional as soon as possible if they develop depression or suicidal thoughts. ^[8]

This does not prove that dutasteride has a lower risk of depression; it means that because fewer reports have been received, and it has been used less often for hair loss. The available psychiatric safety data is much more limited and has less established long-term hair-loss safety data.

The biggest difference between finasteride and dutasteride is by far how long it takes for your body to get rid of them.

Finasteride has a mean terminal plasma half-life of approximately five to six hours in men aged 18–60, increasing to around eight hours in men over 70. With repeated dutasteride 0.5mg dosing, the half-life is approximately three to five weeks. ^[1][2]

A medicine’s half-life is the approximate time taken for the amount in the blood to fall by half. As a rough guide, after one half-life around half would remain, after two around a quarter and after three around an eighth. The actual elimination of a medicine from your bloodstream is more complicated than that simple calculation, but it shows why dutasteride can remain in the body for several months after regular treatment is stopped.

Dutasteride also gradually accumulates with daily use. Its serum concentration reaches approximately 65% of its steady-state level after one month, 90% after three months and its stated steady-state concentration after around six months of taking 0.5mg daily.

It doesn't mean dutasteride takes six months to begin reducing DHT. Its effect on serum DHT is already substantial within the first one to two weeks. In the same way, finasteride’s shorter half-life does not mean its effect on your hair disappears six hours after taking a tablet. Finasteride begins suppressing DHT within 24 hours. Both medications will take months to show visible changes to hair, due to hair follicles growing in cycles measured in months. ^[1][2]

The half-life is important when it comes to stopping the medication for whatever reason. If you stop finasteride, the amount of medicine circulating in your blood falls relatively quickly. If you stop dutasteride after taking it regularly, no new medicine is being added, the dutasteride that has already accumulated will clear gradually over the following weeks and months.

This does not mean a side effect from finasteride will necessarily disappear within a day, or that a side effect from dutasteride will last for months. A medicine’s half-life cannot predict exactly when an individual symptom will improve. However, it does mean that exposure to dutasteride cannot be reversed as quickly if you decide that the treatment does not suit you.

Dutasteride’s long half-life does not make it an inherently bad or dangerous treatment and can come in handy if you ever forget to take a dose or two; it is less likely to matter with dutasteride. It does, however, make starting it a slightly more "risky" treatment to start with if you don't know how you will respond to DHT-blockers due to the length of time it takes to be fully cleared from your system.

The clinical trials tell us which medicine produces the better average result. They do not mean that every man should automatically start with dutasteride.

For many men using a DHT blocker for the first time, finasteride is the more straightforward starting option. Finasteride 1mg is licensed in the UK for male pattern hair loss, has clinical data extending over several years and leaves the bloodstream much more quickly if treatment needs to be stopped. Dutasteride is more powerful and generally performed better in the head-to-head trials, but its use for hair loss is off-label and most direct comparisons with finasteride lasted only 24 weeks. ^[1][2][3][4]

That does not make finasteride a compulsory stepping stone before dutasteride. A prescriber may still consider dutasteride as a first treatment after discussing its stronger DHT suppression, potential benefits, side effects and long half-life.

If you have never tried a DHT blocker before, Finasteride will often be the more standard medicine to start with. It may provide enough DHT suppression to stabilise your hair without immediately choosing the longest-lasting and most powerful option. When deciding whether to change, it needs to be given enough time. It can take around 3-6 months but up to a year before evidence of stabilisation can be expected. Visible regrowth may take longer, and judging the treatment after a few weeks tells you very little about whether it is working. ^[1]

Before starting, take clear photographs of your hairline, temples, crown and parting. Repeat them in the same room, under the same lighting, with the same hairstyle and from the same angles. The number of hairs you notice in the shower and mirror can vary considerably; comparable photographs are much more useful for establishing whether your hairline or density is genuinely changing.

Do not mistake a lack of regrowth for a lack of benefit. The main purpose of a DHT blocker is to slow or stop further follicle miniaturisation. In long-term studies, untreated men continued to lose hair, while men taking finasteride maintained substantially more of it. Keeping roughly the same hairline and density over several years can therefore be a successful treatment result, even if previously bare areas have not filled back in.

Switching to dutasteride may produce some additional growth because it performs better on average in the comparison trials. However, there is no guarantee that the difference will be noticeable for someone whose hair loss is already well controlled. A switch also means accepting an off-label treatment that remains in the body for much longer. If finasteride is well tolerated and your photographs show that you are no longer losing ground, there may be no particular problem for dutasteride’s additional strength to solve.

Now if you are still losing hair on finasteride, and you have:

1. Taken finasteride consistently.
2. Used it for long enough to assess properly.
3. Compared photographs taken under similar conditions.
4. Continued to show a receding hairline or reducing density.

You could consider swapping to dutasteride. Where male pattern hair loss is still progressing despite a proper trial of finasteride, the evidence suggests dutasteride offers a greater chance of additional benefit. It still cannot guarantee recovery of follicles that have already become severely miniaturised or disappeared. ^[3][4]

As both medicines inhibit 5-alpha-reductase and can cause similar sexual or psychiatric side effects, some people may tolerate one better than the other, but there is no reliable way to predict that in advance.