Finasteride is a generic prescription drug used to treat benign prostatic hyperplasia and male pattern baldness. Finasteride can cause side effects that range from mild to serious. Examples include breast enlargement and decreased sex drive.

Finasteride is an oral tablet prescribed to treat benign prostatic hyperplasia and male pattern baldness in adult males.* It’s also available as the brand-name drugs Proscar and Propecia.

Keep reading to learn about the common, mild, and serious side effects finasteride can cause. For a general overview of the drug, including details about its uses, see this in-depth finasteride article.

* In this article, we use the term “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Some people may experience mild to serious side effects during finasteride treatment. Examples of the drug’s commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section.

Mild side effects have been reported with finasteride. These include:

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop taking finasteride unless your doctor recommends it.

Finasteride may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

* To learn more about this side effect, see the “Side effects explained” section.

Serious side effects have been reported with finasteride. These include:

If you develop serious side effects while taking finasteride, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about long-term and permanent side effects of finasteride, see the “Side effects explained” section.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with finasteride, visit MedWatch.

ALLERGIC REACTION

For some people, finasteride can cause an allergic reaction. This side effect wasn’t reported in the drug’s studies but has been reported since the drug was approved for use.

In general, symptoms of an allergic reaction can be mild or serious.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should keep taking finasteride.

If you have symptoms of a severe allergic reaction, such as swelling or difficulty breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to finasteride, they may have you switch to a different treatment.

Get answers to some frequently asked questions about finasteride’s side effects.

Are the side effects of finasteride different in men than in women?

Finasteride is used to treat benign prostatic hyperplasia and male pattern baldness in adult males.* The drug is not approved for use in females* so side effects in women aren’t well known.

However, in some cases, finasteride may be used off-label to treat female pattern hair loss. (Off-label use is when a drug is prescribed to treat a condition other than those it’s approved for.)

Some finasteride side effects reported in studies of females taking oral doses include:

  • decreased sex drive
  • irregular menstruation
  • headache
  • irregular body hair growth

Common side effects of finasteride reported in studies of males include:

  • breast tenderness
  • breast enlargement
  • impotence
  • reduced sex drive*
  • ejaculation disorder

To learn more about possible differences in finasteride side effects in men and women, talk with your doctor.

* In this article, we use the terms “male” and “female” to refer to someone’s sex assigned at birth. For more information about the difference between sex and gender, see this article.

Are some finasteride side effects permanent?

Some finasteride side effects may be permanent. This drug has both mild and serious side effects. Mild side effects are usually temporary and typically go away with continued treatment. Finasteride may also cause some serious side effects which may be permanent and have long-term effects.

These include:

  • prostate cancer
  • depression
  • sexual problems, including erectile dysfunction and reduced sex drive
  • anxiety
  • breast cancer
  • suicidal thoughts

Talk with your doctor to learn about ways you may be able to reduce side effects of finasteride.

Do finasteride side effects include hair loss?

No. In fact, a lower dosage of finasteride (such as what’s in the brand-name drug Propecia) is approved for male pattern baldness. The common side effects of both versions of finasteride are similar and include reduced sex drive, erectile dysfunction, and ejaculation disorder.

For more information about finasteride’s uses and side effects, talk with your doctor or pharmacist.

Help is out there

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

  • Call or text the 988 Suicide and Crisis Lifeline at 988 or chat at 988lifeline.org. Caring counselors are available to listen and provide free and confidential support 24/7.
  • Text HOME to the Crisis Text Line at 741741 to connect with a volunteer crisis counselor for free and confidential support 24/7.
  • Not in the United States? Find a helpline in your country with Befrienders Worldwide.
  • Call 911 or your local emergency services number if you feel safe to do so.

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you’re not in the same household, stay on the phone with them until help arrives.

Learn more about some of the side effects finasteride may cause.

Reduced sex drive

You may experience a decrease in your sex drive when taking finasteride. Reduced sex drive was a common side effect reported in the drug’s studies.

What might help

If you experience reduced sex drive during finasteride treatment and it’s bothersome, talk with your doctor. They can recommend options to increase your sex drive. If this side effect is serious, your doctor may recommend switching you from finasteride to a different treatment.

Postural hypotension

Finasteride side effects include postural hypotension. This is when your blood pressure suddenly drops when you stand up. This was a common but mild side effect reported in the drug’s studies.

Symptoms may include:

What might help

When taking finasteride, stand up slowly from sitting or lying down to lower your risk of a sudden drop in blood pressure.

If you experience ongoing or bothersome low blood pressure, call your doctor. They can recommend ways to help manage this side effect.

Keeping track of side effects

During your finasteride treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start a new drug or combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Sharing notes with your doctor will help them learn more about how finasteride affects you. They can then use this information to adjust your treatment plan if needed.

Finasteride can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether this drug is a good treatment option for you.

Talk with your doctor about your health history before taking finasteride. Be sure to tell them if any of the following factors apply to you:

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.