Finasteride Side Effects, Warnings, and Uses

Published February 5th, 2021 by Chris Riley
Fact Checked by
Camille Freking
Medically Reviewed:
Gerardo Sison
Updated Date: Jun 22nd, 2022

According to the American Hair Loss Association, 95 percent of hair loss in men is caused by male pattern baldness, also known as androgenic alopecia.

Male pattern baldness is passed down genetically and can cause hair to thin on the crown of the head in addition to a receding hairline.

Far from being a condition that just affects older men, male pattern baldness can occur at any age. 

In fact, 25 percent of men who experience male pattern baldness begin to lose their hair before turning 21.

By the time they have reached the age of 35, an estimated two thirds of American men will have significant hair loss, and 85 percent will have experienced significant hair loss by the age of 50. 

Male pattern baldness can be embarrassing and many men suffer from a loss of self confidence as they begin losing their hair. 

However, there are topical and oral treatments available, including oral finasteride.

We’ll go over finasteride side effects, warnings, and uses as well as the evidence supporting finasteride’s ability to stop hair loss and promote hair regrowth. 

What is finasteride?

Finasteride is a prescription medication (unavailable over the counter) that is best known for treating male pattern hair loss and is also used for the treatment of enlarged prostate (benign prostatic hyperplasia).

Finasteride is a generic drug, and the brand name version, Propecia, is well known. 

The medication product is available in the form of an oral tablet and was not originally intended for the treatment of hair loss.

Instead, finasteride was developed for the treatment of benign prostatic hyperplasia. 

During clinical trials, researchers noticed that study subjects suffering from male pattern baldness had reduced hair loss and increased hair regrowth as a side effect of the medication. 

Since the results of the study, additional research has shown that finasteride has the ability to effectively treat male pattern baldness, also known as androgenetic alopecia.

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How does finasteride work?

Finasteride belongs to a class of drugs called 5-alpha-reductase inhibitors.

These medications work by inhibiting the activity of 5-alpha-reductase, an enzyme that is responsible for converting testosterone into androgen dihydrotestosterone (DHT). 

Among the many effects DHT has on the body, it shrinks the hair follicles, which causes the hair to fall out and prevents regrowth.

Additionally, DHT causes the prostate to increase in size, which is why finasteride was originally intended as a treatment for enlarged prostate.

Androgenetic alopecia, also known as male pattern baldness, occurs as a result of elevated DHT levels in men who are genetically predisposed to the condition. 

Finasteride works to promote hair regrowth and stop hair loss by lowering the amount of DHT in the scalp by up to 60 percent, which prevents the shrinking of hair follicles.

Currently, lowering the levels of DHT in the scalp is the only clinically proven way to stop hair loss caused by male pattern baldness.

Does finasteride work?

Finasteride is the only FDA-approved prescription treatment for hair loss.

Several studies have shown that finasteride is clinically proven to be effective in stopping hair loss and encouraging hair regrowth for many men. 

Most studies on finasteride have been conducted using a dose of 1 mg per day, as this is the amount needed to see hair regrowth and stop hair loss.  

A study conducted in 1999 found that taking 1 mg of finasteride orally each day promotes hair growth and prevents further hair loss in 48 percent of study participants in one year and up to 66 percent in two years. After two years, 83 percent of participants receiving finasteride showed no further hair loss compared to 28 percent of those receiving the placebo.  

In addition to being effective at reversing male pattern baldness, finasteride is also well tolerated and doesn’t cause side effects for most people, making it a popular choice for men suffering from male pattern baldness.

Side effects associated with finasteride

Most people tolerate finasteride well when taking the recommended dose of 1 mg per day for hair loss, but some people do experience side effects.

These adverse effects of finasteride are the same regardless of whether the medication is taken for hair loss or enlarged prostate but are more likely to occur at higher doses.

Mild side effects associated with finasteride include:

  • Skin rash
  • Trouble getting or keeping an erection (erectile dysfunction)
  • Decreased sex drive (sexual dysfunction)
  • Sexual side effects such as ejaculation disorder or reduced ejaculate
  • Breast enlargement and tenderness to the touch

Most people find that the side effects of finasteride gradually disappear over several days or weeks as their body adapts to the effects of the medication and the lower DHT levels that result from use of the drug.

Patients who experience these side effects in a severe form or for an extended period of time should contact their doctor.

Side effects, especially those associated with sexual function, usually subside with discontinuation of the medication, but if they don't, seek medical advice from a healthcare professional.

While most side effects caused by finasteride are mild, some adverse events can be serious and potentially life threatening.

Patients experiencing any of the following side effects should contact a doctor right away and should contact 911 if their symptoms feel life threatening.

  • Depression
  • Nipple discharge
  • Swelling of your lips, tongue, throat, or face
  • Lumps or pain in your breasts
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Are there any potential risks associated with the use of finasteride?

Finasteride is generally well tolerated, but there are several warnings associated with use of the medication.

People who are allergic to finasteride or any of its ingredients may experience a severe allergic reaction as evidenced by symptoms that can include trouble breathing, hives, and swelling of the throat or tongue.

Patients experiencing any of these symptoms should call 911 or go to the nearest emergency room for treatment. 

Finasteride can be transmitted through the skin when touched, and the medication can cause birth defects to occur.

Therefore, pregnant women or women are planning to become pregnant soon should not touch finasteride.

The medication is not approved for use in women and should not be handled by women who have the potential to become pregnant due to the risk of abnormalities. Although it is not known whether finasteride can pass through breast milk, women who are nursing should also not use or handle finasteride. 

Finasteride has not been shown to be linked to infertility, but there have been some incidences that suggest it can induce the development of breast cancer. 

One serious cause for concern associated with finasteride is its potential to increase the growth rate of high-grade prostate cancer and cause irregular forms of prostate cancer to develop.

As a result, men who have prostate cancer, have previously had prostate cancer, or who have a strong family history/increased risk of prostate cancer should discuss their medical history with their doctors before using finasteride.

Finasteride is processed in the liver, so people with liver disease or poor liver function should use caution when taking the medication.

Poor liver function can cause the medication to be processed more slowly than usual, which can increase the risk of experiencing side effects and can increase the severity of side effects.

Your doctor may choose to lower your dose of finasteride to minimize this possibility. 

Can finasteride be used to treat hair loss in women?

Finasteride has been clinically proven to treat hair loss in men, but can the drug be equally effective for women? Although finasteride is not FDA-approved for use in women, some studies investigating the potential for the medication to stop hair loss in women have been conducted. 

These studies found treating women with the standard recommended dose of finasteride for men, 1 mg per day, was not effective in stopping hair loss or promoting hair regrowth.  However, when given at a higher dose of 2.5 mg, another study found that 95 percent of study participants experienced at least some improvement when using  the medication, with 65 percent experiencing significant improvement. 

The studies also found that taking an even higher dose of the medication, 5 mg per day, did not improve the likelihood of experiencing improvement and was simply more likely to cause side effects. At this time, finasteride is not recommended for use in women until more studies can be conducted.


Finasteride is an effective oral prescription medication treatment for hair loss caused by male pattern baldness, but it is associated with some side effects and warnings for use.

Men who have had prostate cancer or currently have prostate cancer should not use finasteride, and the medication is not recommended for use in women. 

Finasteride is available in both brand name and generic forms of the drug and can easily be purchased at your local pharmacy with a doctor’s prescription.

Research, Studies and Sources:

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