Common finasteride side effects explained

What should finasteride do?

Finasteride is used to prevent hair loss and to help promote hair regrowth in men with androgenetic alopecia (male pattern baldness). 

The NHS states that you can typically expect to see some improvement to hair loss within 3-6 months of starting your finasteride treatment for male pattern baldness. 

Finasteride is also prescribed under the brand name Propecia.

How effective is finasteride?

Studies into the effectiveness of finasteride show that 83% of men taking 1mg finasteride tablets experienced a reduction in hair loss and increased hair growth after a year of treatment. 

Finasteride also comes as a topical solution, with studies showing its effect to be similar to oral finasteride, but with a lower risk of systemic side effects (side effects which occur in the entire body rather than just in the area applied).

How common are finasteride side effects?

These side effects of 1mg finasteride may affect up to 1 in 100 people:

• Problems with achieving or maintaining an erection

• Problems with producing semen, such as a reduction in the amount produced

• A decreased sex drive

• Depression

These side effects can occur even after finasteride use has been discontinued, but they usually improve within weeks to a few months.

If your side effects don’t improve or cause you discomfort, please arrange an appointment with your GP.

Who is at a high risk of experiencing side effects?

Men with depression, suicidal thoughts and erectile dysfunction are at risk of their symptoms worsening. The UK Government has issued an updated warning (11th May 2026) to men to raise awareness of the sexual and psychiatric side effects of finasteride. 

It's important to discuss your sexual and psychiatric health with your GP first, to make sure finasteride is a suitable treatment for you.

If you develop depression or suicidal thoughts while taking finasteride 1mg, stop taking it and contact a doctor or clinician as soon as possible. If you have seriously harmed yourself or feel at risk of serious harm, call 999 immediately. 

Women must not take finasteride as it has not been medically approved. Finasteride can harm an unborn baby if handled or taken during pregnancy, particularly affecting the development of male genitalia. Our guide ‘Common hair loss treatments for women’ can help women find a more suitable treatment for female hair loss.

What are the most common topical finasteride side effects?

Topical finasteride is less likely to cause side effects that affect the whole body, such as erectile problems or low mood. This means it may be a better option for men who are concerned about these kinds of effects from oral tablets. 

Whilst allergic reactions to topical finasteride are rare, they can still occur and can include reactions such as irritation, itching and burning. 

If you have an allergic reaction to topical finasteride you must seek urgent medical attention. 

Topical finasteride is generally deemed a safe and effective treatment, available only with a private prescription.

How can the side effects of finasteride be reduced?

Finasteride tablets for the treatment of male pattern baldness are only available in a 1mg strength. The 5mg finasteride tablets are only available to treat benign prostatic hyperplasia (enlarged prostate). Since 5mg finasteride tablets are a higher strength, they come with an increased risk of side effects.

Always take finasteride exactly as prescribed, and follow the instructions in the patient information leaflet to help manage your risk of side effects.

If you miss a dose of finasteride and remember within 6 hours, take the missed dose. If it has been longer than 6 hours, skip this dose and carry on as normal the next day. It’s important not to take more than the specified dose as this won’t improve finasteride’s effectiveness but may increase your chance of experiencing side effects.

To reduce your risk of experiencing systemic side effects, you may be better suited to using topical finasteride. Your GP or Clinician will help give you the information you need to make an informed decision.

Is finasteride the right treatment for you?

If you are eligible for treatment and have no known allergies or health conditions that would put you at risk of experiencing side effects, finasteride is generally effective and well-tolerated.

At Pharmacy2U, we have a range of guides on hair loss and the available treatments if you would like to learn more about the available hair loss treatments for men.