Finasteride side effects: what the research actually says

Finasteride side effects get a lot of attention online, some of it accurate and some of it frightening without context. Here is the balanced picture, so you and your doctor can weigh it for your situation.

If you're on finasteride and have low mood, anxiety or thoughts of self-harm, stop and speak to a doctor now. For thoughts of self-harm, call 112 or Tele-MANAS on 14416.

The headline numbers

• Most men have no side effects.
• In the main trials, sexual side effects were reported by a few percent of men on finasteride, compared with a slightly smaller percentage on placebo. The extra risk from the drug itself was about 1–2 in 100 men.
• In the trials, most of these effects went away after stopping, and in many men they went away while continuing.

Sexual side effects

• Why they happen: DHT plays a role in sexual function. Lowering it can affect libido, erections or ejaculate volume in a minority of men.
• The "nocebo" effect is real. In one study, men told about possible sexual side effects reported them more often than men who weren't told. That doesn't mean side effects are imaginary. It means anxiety affects what people experience, and it's worth discussing openly with your doctor.
• What to do: if side effects appear, talk to your doctor. Options include stopping, lowering the dose, or switching to topical finasteride, which reaches the bloodstream in smaller amounts.

Mood, depression and suicidal thoughts

• Regulators have added warnings about depression and suicidal thoughts to finasteride information, based on reports from people taking it.
• The overall risk appears low, but it's taken seriously.
• If you have a history of depression or anxiety, tell your doctor before starting. Ask a partner or family member to tell you if they notice a change in your mood.

Post-finasteride syndrome (PFS)

Some men report sexual, mental or physical symptoms that continue after stopping finasteride. The research here is limited and debated:

• Its causes, and how many men are affected, aren't well established.
• Patient groups and some regulators recognise that persistent symptoms have been reported.
• Our view: the risk appears to be small, but it isn't zero and isn't fully understood. That's why finasteride should be a decision you make with a doctor, not something bought online without a prescription.

Fertility

• Finasteride can lower semen volume and sperm count in some men. This usually recovers after stopping.
• Trying for a baby? Tell your doctor. Some men pause finasteride while trying to conceive.
• Finasteride in semen is not considered a meaningful risk to a pregnancy, but pregnant women must not handle crushed or broken tablets.

PSA tests (men over 40)

Finasteride lowers PSA, a blood test used to screen for prostate cancer, by about half. Always tell your doctor you take finasteride before a PSA test so the result can be interpreted correctly.

Topical finasteride: fewer side effects?

Topical finasteride lowers blood DHT less than tablets, so side effects throughout the body may be less likely. It is not side-effect-free, and long-term data is still limited. → Topical finasteride

Lowering your risk

1. Get a proper diagnosis and prescription. Don't buy finasteride without one.
2. Tell your doctor about any mental health history, sexual health concerns or plans for a baby.
3. Use the standard 1 mg dose. Don't split 5 mg tablets without medical advice.
4. Review with your doctor at around 3 and 6 months, sooner if anything changes.

See a doctor soon if you have: round bald patches that appear suddenly · hair coming out in clumps · redness, pain, pus, scaling or scarring on the scalp · hair loss with fever, weight loss, irregular periods, acne or new facial hair · eyebrow or eyelash loss · hair loss in a child.

Back to: Finasteride guide · Brands and prices · Minoxidil vs finasteride

Sources

1. Kaufman KD, et al. J Am Acad Dermatol. 1998;39:578–89.
2. Mondaini N, et al. Finasteride 5 mg and sexual side effects: how many of these are related to a nocebo phenomenon? J Sex Med. 2007;4:1708–12.
3. Propecia prescribing information (FDA), incl. 2022 label update.
4. EMA PRAC review of finasteride and dutasteride and suicidal ideation (2025).
5. MHRA Drug Safety Update on finasteride: psychiatric and sexual side effects; patient alert card (2024).

Medical review pending: not yet reviewed by a dermatologist. Medical disclaimer