Finasteride

Finasteride is a prescription-only active ingredient against hereditary hair loss in men. It inhibits an enzyme that converts testosterone into dihydrotestosterone (DHT), the most important driver of this form of hair loss. The 1 mg tablet and a topical spray are approved in Germany for hereditary hair loss in men, both prescription-only. The active ingredient preserves existing hair and slows further loss; it only works as long as you use it.

How does finasteride work?

Finasteride is used for hereditary hair loss (androgenetic alopecia), the most common form of hair loss in men. The trigger is the sensitivity of the hair roots to the hormone dihydrotestosterone, DHT for short. DHT gradually causes sensitive hair follicles to shrink; the hairs become thinner, shorter and eventually fall out. You can read exactly how this connection works under DHT and hair loss.

Finasteride belongs to the group of 5-alpha-reductase inhibitors. It mainly blocks type II of this enzyme, which converts testosterone into DHT. This lowers the DHT level in the scalp and blood, and the damaging effect on the hair follicles decreases.¹ Unlike minoxidil, which acts on the hair cycle, finasteride intervenes in the hormone metabolism.

Important for realistic expectations: finasteride slows the loss and can strengthen weakened hairs. It is not a miracle. It does not bring back completely dead hair roots at already bald spots. This is why treatment works better the earlier it begins, as long as active follicles are still present.

What finasteride can achieve

Finasteride is one of the best-studied active ingredients against hereditary hair loss in men. In the approval studies with the 1 mg tablet, about 90 out of 100 treated men showed no further visibly progressing hair loss over five years: some improved visibly, while in the others the condition remained stable. In the placebo group, by contrast, hair loss continued to progress in the majority.²

Two things can be derived from this. Finasteride stops or slows the loss in a large proportion of men. And the most important effect is preservation: keeping hair that would otherwise have fallen out is more realistic than significant regrowth.

If finasteride alone is not enough, there are other active ingredients that a doctor can prescribe, some outside their approval (off-label). You can read how a switch can look under switching from finasteride to dutasteride.

How is finasteride used and is it approved?

Finasteride is available against hereditary hair loss in two forms, both prescription-only.

The oral tablet with 1 mg of finasteride is approved in Germany for the treatment of hereditary hair loss in men. You take it once a day, regardless of meals.

A topical finasteride (spray) is also approved in Germany for men with hereditary hair loss and is prescription-only. You apply it to the scalp. Because the active ingredient acts predominantly locally, less of it reaches the bloodstream than with the tablet.³ Which form is an option depends on your situation, tolerability and your preference. In pronounced hair loss, doctors sometimes combine finasteride with minoxidil, which acts at a different point.

Both forms can be prescribed by a doctor if a treatment is medically suitable. Whether finasteride suits you is checked by our doctors based on your health information. A doctor may also prescribe an approved medication outside the approved area of application in an individual case (off-label) if they weigh benefit and risk.

Side effects

Most men tolerate finasteride well. In a minority, side effects occur that are related to the intervention in the hormone metabolism.

The main ones are sexual dysfunctions:

• Decreasing libido: reduced sexual desire.
• Erectile dysfunction: an erection is harder to achieve or maintain.
• Changes in ejaculation: for example a smaller amount of ejaculate.

These complaints resolve in most men when finasteride is stopped, in some also while continuing use. However, there are reports in which sexual dysfunctions persisted for a longer time after stopping.⁴

Mood changes are also possible, including depressive mood. What you should watch out for is described under Warnings.

Persistent complaints after stopping are discussed under the term post-finasteride syndrome. Whether it is a distinct clinical condition and how common it is has not yet been scientifically clarified. Nevertheless, take new or persistent complaints seriously and discuss them with a doctor. You can find a detailed overview under Finasteride and side effects.

Interactions and contraindications

Finasteride must not be used in cases of known hypersensitivity to the active ingredient or to one of the other components.

The most important contraindication concerns women of childbearing age and during pregnancy. Finasteride can disturb the development of the external genital organs of a male fetus. Therefore, pregnant women must neither take finasteride nor come into contact with broken or crushed tablets, since the active ingredient can be absorbed through the skin. Whole, undamaged tablets have a film coating that prevents contact with the active ingredient during normal handling. More on this under Finasteride, family planning and pregnancy.

For the tablet, no significant interactions with other medications are known so far. Nevertheless: tell us your pre-existing conditions and all the agents you take in the health questionnaire. This is how our doctors check whether finasteride is suitable in your case.

Warnings

Authorities such as the BfArM and the European Medicines Agency EMA explicitly point out sexual and psychological side effects with finasteride.

A Red Hand Letter from 2018 names reports of mood changes, including depressive mood, depression and suicidal thoughts.⁴ In 2025 the warnings were tightened: anyone who notices depressive mood, depression or suicidal thoughts while using oral finasteride for hair loss should stop use and seek medical advice.⁵ If you notice such changes in yourself, take them seriously and consult a doctor.

Finasteride also lowers the PSA level in the blood, by about 40 to 50 percent. The PSA level is used for the early detection of prostate cancer.⁶ If a PSA test is due for you, tell the doctor that you are using finasteride, so that the value is interpreted correctly.

Keep finasteride out of the reach of children.