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Home / Hair Loss / Finasteride side effects: what to expect

Finasteride side effects: what to expect

Learn more about the side effects of finasteride

Finasteride, or Propecia, is an effective treatment for male pattern hair loss (androgenetic alopecia).

It works by preventing the body from turning testosterone into dihydrotestosterone (DHT). This hormone causes hair follicles to shrink and ultimately results in hair loss in the long term.

Close-up of man reading patient leaflet with medication.

While effective, it can cause some side effects in some men. So if you’re interested in taking Finasteride tablets, it’s important to know what to expect.

Keep reading to learn more about the potential side effects and how to reduce the side effects of finasteride.

What are the common side effects of Finasteride?

The most common side effect of Finasteride is sexual dysfunction.

Men may experience:

These symptoms are caused by increased levels of oestrogen.

Close-up of man with hands over his crotch.

This is because Finasteride prevents testosterone from being converted into DHT, which means more testosterone is converted into estradiol (a type of oestrogen). So, testosterone levels are reduced.

What are the uncommon side effects of Finasteride?

Breast abnormalities

Yes, men can experience breast changes as much as women can. This can occur whilst taking Finasteride as it increases oestrogen levels.

In some men, this can cause a condition called gynaecomastia. It is a condition that makes men’s breasts appear more like female breasts.

Close-up of man covering his chest shirtless.

Symptoms can range in severity. Most commonly, men experience extra tissue around the nipples. In more severe cases, men may notice more breast tissue (like female breasts), pain or tenderness.

Skin reactions

Some men may experience an allergic reaction if they have not taken Finasteride before. Symptoms may include:

  • itchy rash
  • redness
  • irritation
  • hives

If you notice any of these symptoms, stop taking Finasteride and consult your doctor.

What are the serious side effects of Finasteride?

Some side effects are extremely rare, so much so their frequency is unknown. Rare side effects usually occur from 1 in 1000 to 1 in 10,000 cases.

However, it’s important to know in the very rare chance you develop any of these side effects.

Rare side effects include:

  • angioedema (swelling caused by fluid build-up)
  • infertility
  • palpitations
  • testicular pain
  • depression
  • suicidal thoughts

Breast cancer

There have been some reports of male breast cancer on Finasteride. However, studies Trusted source UK Government Publications Government Source Go to source have shown there is no significant difference in breast cancer rates between men who take Finasteride and men who don’t.

However, you should still check for breast abnormalities. Talk to your doctor if you spot any breast cancer symptoms such as lumps, breast changes, tenderness or nipple discharge.

How long do side effects last?

In most cases, if you experience side effects, they should only last for a few weeks. This is normal as your body adjusts to the medicine. However, if you continue to experience side effects speak to your doctor or pharmacist.

What cautions should I take whilst on Finasteride?

As well as side effects, there are some precautions to take whilst on Finasteride.

Pregnant women

Finasteride can affect an unborn baby. So, pregnant women should not handle crushed or broken tablets. Men should also wear barrier contraception whilst taking Finasteride.

Laboratory tests

Finasteride can also affect some lab tests. In particular, it can reduce the serum content of prostate cancer markers. Let your doctor know if you are using Finasteride.

What happens when I stop taking Finasteride?

Some men experience side effects when they stop taking Finasteride.

This is known as post-finasteride syndrome (PFS). Little is known about the condition, and research is ongoing.

It causes both physical and mental symptoms. In 2021, the first-ever diagnostic criteria were published on it in the medical literature.

Below are all the reported symptoms of PFS.

Sexual symptoms Physical symptoms Mental or cognitive symptoms
  • low sex drive
  • erectile dysfunction
  • loss of pleasurable orgasms
  • decreased semen volume
  • penile and/or scrotal shrinkage
  • Peyronie’s disease
  • gynaecomastia
  • fatigue
  • muscle pain or weakness
  • changes in skin texture
  • vision changes
  • metabolism changes
  • tinnitus
  • memory problems
  • depression, anxiety and suicidal thoughts
  • emotional flatness
  • insomnia
  • obstructive sleep apnoea (OSA)

Unfortunately, there is no cure and few effective treatments for this condition. Thankfully, it is quite rare.

In 2018 Trusted source National Center for Biotechnology Information (NCBI) Government Source Biomedical Research and Literature Go to source , it was estimated over 1000 men worldwide were experiencing symptoms of PFS. This was based on an internet advice forum for people on Propecia. However, it is likely the condition is underdiagnosed as little is known about it.

For more information and support, consult the PFS Foundation website.

Who is more at risk of side effects?

If you have other health conditions or take any other medication, ask your doctor or pharmacist before using Finasteride. This is because you may be at a higher risk of side effects.

Ask your doctor first if you:

  • have a history of depression or mental illness
  • have obstructive uropathy (a condition that prevents urinary flow)
  • are lactose intolerant
  • have a history of ED or another sexual disorder

It may be safe for you to take, but you should always ask a healthcare professional for medical advice.

How do I manage the side effects of Finasteride?

Some side effects can be managed with other treatments.

For example, if you experience erectile dysfunction there are several prescription treatments available to you including Viagra.

Learn more about ED treatment

Click here

However, in some cases, it may be better to switch to an alternative treatment option.

An equally effective alternative to Finasteride is Minoxidil. It is a topical treatment that you apply directly to the areas experiencing hair loss. You can get it over the counter or on prescription.

Medically reviewed by Dr. Caroline Fontana Written by our editorial team Last reviewed 05-07-2024

Further reading

Common causes of hair loss: a complete guide

Common causes of hair loss: a complete guide

Reviewed by Dr. Caroline Fontana
The most common finasteride results - what should I expect?

The most common finasteride results - what should I expect?

Reviewed by Dr. Caroline Fontana
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