Dutasteride

Dutasteride comes from the same group of active ingredients as finasteride, the 5-alpha-reductase inhibitors. It lowers the level of the hormone dihydrotestosterone (DHT), which causes the hair follicles to shrink in hereditary hair loss. The most important point up front: in Germany, dutasteride is not approved for hair loss. For hereditary hair loss it is therefore used exclusively off-label and is prescription-only in any case.

How does dutasteride work?

Dutasteride is discussed for hereditary hair loss (androgenetic alopecia), the most common form of hair loss in men. In this form, the hair follicles on the forehead and top of the head react sensitively to DHT. Over the years the hormone causes the affected follicles to shrink; the hairs become thinner, shorter and eventually fall out. You can read how this mechanism unfolds under DHT and hair loss.

The enzyme 5-alpha-reductase converts testosterone into DHT. Whoever inhibits this enzyme lowers the DHT level and thereby deprives the follicles of their most important attacker. There are two types of the enzyme, type I and type II. Here lies the difference between the two active ingredients: finasteride mainly inhibits type II, which is active among other places at the hair follicle. Dutasteride inhibits both types and thereby lowers the DHT level in the blood more comprehensively: in studies by around 90 percent or more, while finasteride lowers the serum DHT level by about 70 percent.¹ On the scalp itself the difference between the two active ingredients is smaller than in the blood.¹ You can read how finasteride, as the agent approved in Germany, works on the page Finasteride.

Important for realistic expectations: dutasteride acts on the hormone metabolism and keeps the DHT level low as long as the active ingredient is in the body. It does not change the predisposition itself. The effect therefore only lasts as long as the treatment continues. It does not bring back completely atrophied follicles at already bald spots, which is why treatment works better the earlier it begins.

Is dutasteride approved for hair loss?

No. In Germany, dutasteride is approved only for the treatment of benign prostatic enlargement (benign prostatic hyperplasia).² The active ingredient has no official area of application against hair loss here. If it is nevertheless prescribed for hereditary hair loss, this is done off-label.

For oral intake, dutasteride is available as a prescription-only capsule. You obtain it only with a doctor's prescription, and it is only prescribed if a doctor considers the treatment medically suitable. You can find a more detailed classification of the approval status and the evidence in the article Dutasteride for hair loss.

Dutasteride or finasteride?

At the level of the hormone the answer is clear: dutasteride lowers the DHT level more strongly than finasteride, because it inhibits both enzyme types.¹ Whether this also results in visibly more hair is the more difficult question.

In a randomised comparative study over 24 weeks, hair density in men on dutasteride increased in a dose-dependent manner, at the highest tested dose more strongly than on finasteride.³ Review articles also describe tendentially somewhat larger gains in hair density on dutasteride.⁴ However, this statement is only of limited reliability. The comparative studies mostly ran over a few months and had small numbers of participants. Reliable long-term and safety data specifically for use against hair loss are thinner than for finasteride, for which extensive data over years is available. A greater effect on the hormone therefore does not automatically mean a better result for every user.

For these reasons, dutasteride is not at the start of a treatment. It is discussed above all when finasteride, as the approved agent, has been exhausted and nevertheless does not work satisfactorily. Whether a switch to dutasteride makes sense in an individual case is decided by a doctor. You can read how such a switch proceeds and what is checked beforehand in the article Switching from finasteride to dutasteride. For anyone who does not want to act on the hormone metabolism, minoxidil can be another route, which acts on the hair cycle.

Side effects

Because dutasteride intervenes in the same hormone metabolism as finasteride, their possible side effects are similar. In a minority of men, sexual dysfunctions are possible, such as reduced libido or erectile dysfunction. Less often, mood changes are reported. These complaints usually resolve after stopping, but in individual cases can persist longer and should be clarified with a doctor early.

Two properties distinguish dutasteride from finasteride here:

• Stronger DHT intervention: Dutasteride intervenes more comprehensively in the DHT balance, so hormone-related side effects can be more pronounced.
• Long residence time: The half-life is several weeks, and the active ingredient is still detectable in the blood months after the last intake.¹ If side effects occur, they can therefore persist longer, even after the active ingredient has been stopped.

In 2025 the authorities updated the safety information for this group of active ingredients. A Red Hand Letter confirms depressive mood and suicidal thoughts as a side effect for orally taken finasteride, above all in use against hair loss. For dutasteride the same warning applies as a precaution, because it belongs to the same group of active ingredients. A direct connection has so far not been sufficiently proven for dutasteride.⁵ This is no reason to panic, but a reason to have such a treatment medically supervised and to raise new complaints early.

Interactions and contraindications

Dutasteride is contraindicated in women who are pregnant or could become pregnant. The reason is clear: the active ingredient can disturb the genital development of a male fetus.² For the same reason, women should not touch the capsules if they are damaged, because the active ingredient can be absorbed through the skin. It must not be used in cases of known hypersensitivity to dutasteride or to other 5-alpha-reductase inhibitors.

Because dutasteride is originally used against the prostate, it lowers the PSA level in the blood, a marker of prostate early detection, to about half after a few months.² Anyone who has such checks should inform the treating doctor about taking it; for the assessment the measured value is then usually doubled. Whether a treatment is an option for you and whether it is compatible with your other medications is checked by our doctors based on your health information.

Warnings

The long residence time in the body has consequences beyond the side effects. Because dutasteride can disturb the development of a male fetus, men must not donate blood while taking it and until six months after the last capsule.² The active ingredient also passes in small amounts into the semen; if there is a wish to have children, this, together with the long residence time, should be discussed with the partner and a doctor beforehand.²

The effect achieved is reversible. If dutasteride is stopped, the DHT level rises again over some time, and hair loss continues where it would stand without treatment. Because of the long residence time this happens more slowly than with finasteride. A planned stop is best discussed with a doctor.