Finasteride: How It Works, Benefits and Side Effects

Finasteride is a prescription-only tablet for hereditary hair loss. It works by inhibiting the conversion of testosterone into the hormone dihydrotestosterone (DHT). In people with the corresponding predisposition, DHT gradually causes the hair follicles to shrink, and this is exactly the process that finasteride slows down. The benefit lies above all in preservation: further loss is stopped or slowed, and in some men the density improves again as well.

Whether finasteride is suitable for you depends on your findings, your health and possible contraindications. A doctor makes this assessment. With us you can have this clarified medically and without a long wait.

What is finasteride?

Finasteride is an active ingredient from the group of 5-alpha-reductase inhibitors. For hereditary hair loss it is taken as a tablet at a dose of 1 mg daily.¹ The active ingredient is prescription-only, so you can only get it with a doctor's prescription.

Important for context: for the treatment of hereditary hair loss in men, finasteride is approved in Germany. It is therefore used within its official approval, not off-label. This distinguishes finasteride from some other options. Oral minoxidil, for example, is only an option for hair loss off-label, that is, outside the official approval. What this means and when it matters, you can read in the article Oral minoxidil.

How does finasteride work?

Hereditary hair loss (androgenetic alopecia) is closely linked to the hormone DHT. DHT is formed in the body from testosterone, with the help of the enzyme 5-alpha-reductase. In men with the corresponding predisposition, the hair follicles at the forehead and crown react sensitively to DHT: over time they go through ever shorter growth phases and produce ever finer, shorter hairs. This process is called miniaturization. In the end the follicle produces barely any visible hair.

Finasteride blocks the enzyme 5-alpha-reductase and thereby curbs the production of DHT. At the 1 mg dose, the DHT level in the blood drops by around 70%.¹ Less DHT means less pressure on the sensitive follicles. Miniaturization is slowed, and the affected hair roots get the chance to stabilize instead of shrinking further.

Two things are important to understand here. First, finasteride only works as long as you take it. It does not change the predisposition itself, but keeps the DHT level low for as long as the active ingredient is in the body. Second, finasteride acts on the hormone balance. This is precisely why it is prescription-only and belongs in medical care. How DHT and predisposition interact in hair loss is set out more broadly by the article Understanding hair loss. Details on the active ingredient itself can be found on the page Finasteride.

What finasteride does and what is proven

The efficacy of finasteride is well studied. In controlled studies, hair growth at the crown improved after 2 years in around 2 out of 3 men (66%), while under placebo hair loss usually continued.² Over longer periods, further visible hair loss under finasteride also occurred markedly less often than under placebo.³ These are average values from controlled studies. How strong the effect is for you varies from person to person.

The focus is on preservation. Finasteride above all stops or slows further thinning; in some men the density in the treated area improves again as well. What finasteride cannot do: revive completely inactive hair follicles. If follicles have already atrophied and no longer produce hair, the active ingredient cannot bring them back either. This is why a treatment works better the earlier it begins, as long as there is still hair to preserve.

Patience is part of it. First visible changes usually appear after 3 to 6 months of regular use; a reliable assessment generally takes 6 to 12 months. In the first weeks little often happens on the outside, even though the active ingredient is already working in the background. Anyone who sees no effect after 4 weeks and stops is breaking off the treatment before it can even be judged whether it is working.

Which side effects are possible

Like any effective medication, finasteride can have side effects. Because it intervenes in hormone metabolism, the relevant side effects in a small proportion of users affect sexual function. Possible are a reduced libido, erectile dysfunction or ejaculation disorders. At the 1 mg dose, erectile dysfunction affected about 1 to 2 out of 100 men.¹ In most of those affected, these complaints resolve when the medication is stopped, sometimes even during continued use.

Less often, mood changes such as low mood are reported. Persistent complaints that continue even after stopping are reported in isolated cases. How common this is and how it is connected has not yet been conclusively clarified scientifically; the study data on this is limited. We state this openly so that you can factor it into your decision.

A further point concerns not well-being but a laboratory test: finasteride lowers the PSA value in the blood. This value is used in urological cancer screening. If you are planning such an examination, you should inform the doctor that you are taking it, so that they can interpret the reading correctly.

This weighing of benefit against possible side effects is the reason finasteride is not available without a prescription. A doctor checks before prescribing whether the active ingredient is sensible and safe for you, and remains your point of contact during treatment. If complaints occur, report them early rather than sitting them out. This also includes a rarely possible tightness or enlargement of the breast, which you should have medically clarified.

For whom finasteride is an option

Finasteride for hair loss is prescribed above all to men with androgenetic alopecia whose hair loss follows the typical pattern: slowly progressing, at the receding hairline and crown. Whether it is medically suitable for you is decided by a doctor after reviewing your health information. A prescription is never guaranteed.

For women who are pregnant or could become pregnant, finasteride is contraindicated. The active ingredient can disrupt the genital development of a male fetus. Those affected must not take it and should also avoid skin contact with broken or crushed tablets, because the active ingredient can be absorbed through the skin. Intact, coated tablets, on the other hand, are harmless to simply touch. Because of this mechanism of action, finasteride is prescribed primarily to men. Which causes and treatments play a role in women with hair loss is covered in the article Hair loss in women. Caution is also advised with certain liver diseases or known intolerance. This is why the medical review always comes first, not immediately the prescription.

Finasteride is one of several options

Finasteride is well studied, but not the only route for hereditary hair loss. Also frequently used is topical minoxidil, which is applied externally to the scalp and works locally. Because finasteride acts on the hormone and minoxidil directly on the follicle, the two active ingredients act at different points and are sometimes also combined. Which route fits depends on findings, prior illnesses and your preferences, and is a medical decision. A general comparison of the options therefore does not replace the individual assessment.

If you want to know whether finasteride or another treatment is an option for you, you don't need to bring a finished result. With us you first answer a medical questionnaire about your hair loss and your health. Our doctors review your information and decide whether a treatment is medically suitable, and which. How this assessment works, you can read in the article How the health questionnaire works. What applies to prescriptions in Germany is explained by the article how to get a finasteride prescription in Germany.