Spironolactone (Aldactone) is a type of medication known as an aldosterone receptor antagonist. It’s FDA-approved for treatment of fluid retention caused by a variety of conditions, including liver disease and kidney disease. However, it’s also used to treat other conditions, including:

Recently, some doctors have started prescribing it for female pattern hair loss caused by androgenic alopecia. This is a type of hair loss that’s associated with the overproduction of male sex hormones. Spironolactone is usually only prescribed when other treatments, such as minoxidil, don’t work.

Spironolactone won’t treat hair loss in men. It also won’t work for female hair loss due to nonhormonal causes, such as:

  • stress
  • chemotherapy
  • nutritional deficiencies

Read on to learn more about how spironolactone treats female hair loss, how long it takes to work, and the side effects it can cause.

Spironolactone slows down the production of androgens. These are male sex hormones, including testosterone. Reduced production of androgens can slow down the progression of hair loss caused by androgenic alopecia. It can also encourage hair to regrow.

A 2015 study found that almost 75 percent of participants with female pattern hair loss noticed an improvement in their hair loss after taking spironolactone.

In addition, a 2017 study noted that a combination of spironolactone and minoxidil had significant benefits. This combination was associated with reduced shedding, increased hair growth, and thicker hair.

For hair loss, your doctor will likely prescribe a daily dose of 100 to 200 milligrams. However, they might recommend you start with 25 milligrams a day and slowly increase your dose to reduce your risk for side effects.

Spironolactone sometimes causes drowsiness, so it’s best to take at night. You can take it with or without food.

If you haven’t gone through menopause, your doctor might also prescribe birth control pills to take with spironolactone. They might also prescribe minoxidil to take with spironolactone, regardless of your age.

The exact dosage and combination of medication that your doctor suggests will depend on how severe your hair loss is and whether you take other medications for hair loss or other conditions.

Spironolactone takes a while to start working for hair loss, so don’t be discouraged if you don’t see improvement right away.

Most people need to take it for at least six months before they start seeing results. Others might not notice any benefits until they’ve taken it for at least a year.

Follow up with your doctor after taking spironolactone for six months. Depending on your results, they might increase your dosage or prescribe a different medication to take with or instead of spironolactone.

Spironolactone is commonly prescribed to lower blood pressure and it may cause low blood pressure in those taking it for hair loss. You should regularly check your blood pressure while taking spironolactone, as this can be dangerous if you don’t have high blood pressure. Learn how to check your blood pressure at home.

Other common side effects of spironolactone include:

  • drowsiness
  • nausea
  • diarrhea
  • headache
  • dizziness
  • irregular periods
  • breast tenderness
  • weight gain
  • low sex drive
  • depression
  • fatigue

More serious but less common side effects include:

  • gastrointestinal bleeding
  • high potassium levels

High blood potassium is serious and potentially life-threatening. Call your doctor right away if you notice any of the following symptoms while taking spironolactone:

  • muscle fatigue
  • weakness
  • abnormal heart beat
  • nausea
  • paralysis

Spironolactone is generally safe, but it can lead to health problems if not taken correctly.

Talk to your doctor before taking any other medications while taking spironolactone. That includes nutritional supplements (especially potassium) and diuretics.

Before taking spironolactone, tell your doctor if you’re pregnant or breastfeeding, or have:

Talk to your doctor right away if you become sick while taking spironolactone, especially if you have severe or persistent nausea or vomiting, or diarrhea. These can all cause dangerously low blood pressure when taking spironolactone.

Make sure you drink plenty of water while taking spironolactone, especially in hot weather or during exercise. Know how to recognize the signs of dehydration, which include:

  • extreme thirst
  • infrequent urination
  • dark-colored urine
  • confusion

Get emergency medical treatment if you experience any signs or symptoms of a severe allergic reaction to spironolactone, including:

  • trouble breathing
  • rapid or weak heartbeat
  • seizures
  • loss of consciousness

Spironolactone is an effective treatment for hair loss due to androgenic alopecia in women. However, it can take up to a year to work. If you’re interested in trying spironolactone for hair loss, talk to your doctor. Make sure to tell them about any medical conditions you have and the kinds of hair loss treatments you’ve tried in the past.