Finasteride dosage, forms, and strengths

Finasteride is a prescription drug approved by the Food and Drug Administration (FDA) to treat enlarged prostate (benign prostatic hyperplasia) and male pattern hair loss in men (androgenetic alopecia). Healthcare professionals may prescribe it off-label to prevent prostate cancer or treat unwanted body hair (hirsutism) in women. As an antiandrogen drug, finasteride blocks the body’s conversion of testosterone into its active form, dihydrotestosterone (DHT). Most people will take finasteride tablets, but finasteride is also contained in a topical combination with minoxidil to promote hair growth. People can also purchase a brand-name version of the drug, such as Propecia for male pattern baldness or Proscar for prostate enlargement. Oral doses of finasteride are taken once per day with or without food—one milligram (mg) per day for male pattern baldness and five mg per day for enlarged prostate.

Finasteride forms and strengths

Finasteride by itself is only available as a tablet:

• Tablets: 1 mg, 5 mg

Finasteride dosage for adults

Finasteride is FDA-approved to treat enlarged prostate (BPH) and male pattern baldness in adult males. It may also be prescribed off-label to women who have unwanted body hair typical of a male, a condition called hirsutism. Finasteride is never prescribed to pregnant women. At one time, finasteride was also used off-label to prevent prostate cancer, but healthcare professionals no longer believe that finasteride’s benefits in preventing prostate cancer outweigh the risks.

Finasteride dosage for male pattern baldness

Men using finasteride for hair regrowth will take finasteride 1 mg tablets. Finasteride blocks the body’s production of active testosterone, called DHT. Male pattern baldness is largely due to the sensitivity of hair follicles to DHT. Balding areas of the scalp have more DHT than the parts of the scalp with hair. By decreasing DHT in those areas, finasteride slows hair loss. 

• Standard adult dosage for male pattern baldness: 1 mg taken daily

Finasteride dosage for benign prostatic hyperplasia (BPH)

Men with BPH will take finasteride 5 mg tablets. Like male pattern baldness, an enlarged prostate is also a result of the effects of DHT. Like hair follicles, the prostate is a repository of enzymes that convert testosterone to DHT. Finasteride reduces DHT levels in the prostate by 90%, which over time, causes the prostate to shrink. Treatment will require an initial blood test to measure prostate-specific antigen or PSA levels and assess the person’s risk of prostate cancer.

• Standard adult dosage for BPH: 5 mg taken daily

Finasteride dosage for hirsutism (off-label)

Non-pregnant women with unwanted male-pattern body hair can be treated with finasteride or a combination of finasteride and birth control pills. Antiandrogens such as finasteride, spironolactone, and flutamide are common therapies for hirsutism, but none of them are FDA-approved for this use. Finasteride is a drug of choice because it has fewer side effects and drug interactions than other antiandrogens.

• Standard adult dosage for hirsutism: 5 mg taken daily alone or with oral contraceptives

Finasteride dosage for children

Finasteride is not FDA approved for use in children. Pediatric disorders do not encompass any of the conditions it treats, including male-pattern baldness and enlarged prostate.

Finasteride dosage restrictions

Finasteride does not have dosage restrictions or reductions for kidney impairment or liver dysfunction. However, the FDA warns healthcare professionals to be cautious when prescribing finasteride to men with liver problems. The drug is metabolized by the liver, so men with hepatic impairment have a higher risk of side effects. No dosage restrictions are necessary for older adult men.

Finasteride dosage for pets

Veterinarians use finasteride to treat enlarged prostate in dogs. However, the preferred treatment is castration for animals not being bred or shown. Finasteride treatment is usually long-term. For finasteride therapy to work, doses must be given faithfully each day. Doses may be determined by body weight (0.1 to 0.5 mg per kg of body weight) or more simplified doses as follows:

• 1.5 mg (1/3 of a 5 mg tablet) per day for dogs weighing less than 15 kg (33 lbs)

• 2.5 mg (1/2 of a 5 mg tablet) per day for dogs weighing between 15 kg and 30 kg (33–66 lbs)

• 5 mg for dogs weighing more than 30 kg (66 pounds or more)

How to take finasteride

Finasteride is taken once per day as a tablet. For both male pattern baldness and BPH, dosing compliance is important. If the drug is stopped, hair loss will come back, or the prostate will start growing again.

• Take this medication as instructed.

• Finasteride can be taken with meals or on an empty stomach.

• Do not take more than one tablet per day.

• It is okay to take any other medicine along with the finasteride dose.

• If a dose is missed, skip the missed dose and take the next dose as scheduled on the next day. Do not take an extra finasteride tablet to compensate for a missed dose.

• This medication has a patient information guide containing important instructions and warnings. Please review it before starting the medicine.

Finasteride dosage FAQs

How long does it take finasteride to work?

Finasteride immediately begins to reduce DHT levels in the body. DHT levels in the blood fall immediately and hit their minimum about eight hours after taking the first dose. However, the effects on hair growth or urination symptoms will take several weeks or months to become noticeable. In four-year clinical studies of finasteride for BPH, urinary symptoms noticeably improved in the first few months, but men did not reach maximum symptom relief until the third year of the trials. In 5-year clinical trials of finasteride for male-pattern baldness, men in the trial had noticeable improvements in hair count and appearance by the end of six months and reached their maximum hair count and appearance at the end of the first year. Men taking an inert placebo lost hair throughout the trial period.

How long does finasteride stay in your system?

The half-life of finasteride is about six hours in healthy men. The drug hits its maximum effects on DHT in about eight hours. With a half-life of six hours, it will take about a day for a finasteride dose to become undetectable in the bloodstream.

What happens if I miss a dose of finasteride?

Do not take a missed dose of finasteride if it’s been forgotten. Instead, take the next dose on the scheduled day and time. Do not take extra finasteride tablets to make up for a missed dose. 

How long can you take finasteride?

Finasteride is intended for long-term treatment. Clinical trials continued for five years for both male pattern baldness and prostate enlargement. If finasteride is discontinued without another similar drug being prescribed, the prostate will begin to grow again, and hair will again start to recede. However, even though finasteride is a long-term treatment, people taking finasteride are at an increased risk of developing high-grade prostate cancer, even though it reduces the overall risk of developing prostate cancer. Finasteride also increases the risk of males developing breast cancer because of the change in hormones.

How do I stop taking finasteride?

Discontinuation of oral finasteride will not cause withdrawal symptoms, so the drug can be stopped without gradually reducing the dose. However, the prostate will start growing again, or the hair will start receding again.

What is the maximum dosage for finasteride?

The maximum dosage for finasteride is 5 mg per day.

Can you overdose on finasteride?

There are no reported adverse effects of a finasteride overdose. Animal studies have shown that lethal overdoses are possible, but people have taken high doses without problems. There is no treatment for a finasteride overdose. If too much finasteride is taken, call a poison control center or a healthcare provider for medical advice.

What interacts with finasteride?

Finasteride has no significant drug interactions. Finasteride is considered safe to take with other prescription medications, over-the-counter drugs, herbal remedies, and dietary supplements. However, always discuss all prescription and OTC medications with your healthcare provider.

What happens when you mix finasteride and alcohol?

The FDA does not caution men taking finasteride to avoid alcohol. There is no evidence that alcohol reduces the effectiveness of finasteride treatment or increases the risk of side effects. 

Is it safe to take finasteride during pregnancy?

Finasteride is not safe to take during pregnancy because it can harm male fetuses. It is also not safe for pregnant women to touch or handle finasteride tablets. 

Is it safe to take finasteride while breastfeeding?

Finasteride is not FDA-approved for use by women, regardless of breastfeeding status. No clinical studies have been conducted to assess the presence of finasteride in human milk, its impact on lactation, or its potential adverse effects on a nursing infant. 

When is it not safe to take finasteride?

Finasteride is not safe to take by anyone who’s had allergic reactions to the drug or pregnant women. People with liver disease may have an increased risk of experiencing side effects.

What side effects are possible when taking finasteride?

Finasteride lowers active testosterone levels, so the most common side effects of finasteride are erectile dysfunction, ejaculation disorders, sexual dysfunction, and an increase in breast tissue. Men taking finasteride may also experience dizziness and a sudden drop in blood pressure when standing up. Serious side effects include infertility, severe allergic reactions, and an increased risk of high-grade prostate cancer and breast cancer. Some men taking finasteride have also experienced depression, including suicidal thoughts.

Finasteride or dutasteride for hair regrowth?

Dutasteride is another antiandrogen drug with a mechanism of action similar to finasteride. They both belong to a family of drugs called 5-alpha reductase inhibitors. Studies have shown that dutasteride is more powerful at blocking the conversion of testosterone to DHT, produces better results, and has the same side effects. Ask the prescribing healthcare professional for medical advice about the best treatment before starting antiandrogen therapy.

Sources

• Benign prostatic hyperplasia in dogs and cats, Merck Veterinary Manual

• Finasteride, StatPearls

• Finasteride drug summary, Prescriber’s Digital Reference

• Finasteride tablet 5 mg prescribing information, NIH National Library of Medicine

• Finasteride tablet 1 mg prescribing information, NIH National Library of Medicine

• What is finasteride: Uses, warnings & interactions, SingleCare