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Health Guide / Finasteride

Does finasteride work?

felix gussone

Reviewed by Felix Gussone, MD, written by Rachel Honeyman

Last updated: Apr 14, 2023
5 min read

table of contents

  1. Does finasteride work? 
  2. How does finasteride work?
  3. How long does finasteride take to work?
  4. What is finasteride used for? 
  5. Side effects of finasteride

Hair is often one of the first things we notice about another person. Styling your hair is an avenue of self-expression, and hair can be a part of your identity. So, losing your hair can feel like a blow to your sense of self. If you’re experiencing hair loss, you might be eager to find a quick fix. Unfortunately, there are many gimmicks on the market, so how do you know what really works? 

Finasteride (see Important Safety Information), a medication that’s FDA-approved to treat enlarged prostate, is also approved to treat male pattern hair loss in biological men. And yes, it works: Studies show finasteride does indeed treat and prevent hair loss. Continue reading to learn more.  

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Does finasteride work? 

Good news–finasteride is an effective treatment for preventing further hair loss in those with androgenetic alopecia (AGA, or male pattern hair loss).

Finasteride is an oral medication in a class of drugs called 5-alpha-reductase inhibitors, often known by its brand name, Propecia. In addition to preventing further hair loss in those with AGA, the medication promotes hair regrowth to reverse at least some hair loss for many balding men. Unfortunately, finasteride is only FDA-approved for biologically male patients with AGA. 

Contrary to popular belief, biological women can get androgenetic alopecia, too. It affects up to 38% of women over 70, but other medications are more effective for AGA in women. 

How does finasteride work?

In androgenetic alopecia, excess dihydrotestosterone (DHT) attacks the hair follicles on the head, causing miniaturization of the hair follicles and, eventually, hair loss. Finasteride works by preventing the conversion of testosterone into DHT. 

That same mechanism makes finasteride effective at treating benign prostatic hyperplasia (BPH), too. In BPH, the prostate gets enlarged, and finasteride helps shrink the prostate’s size by decreasing DHT levels. 

How long does finasteride take to work?

Men using finasteride for hair loss may see results in as little as three to four months. However, they typically see significant results after one year of use. In a clinical trial, men with an average of 876 hairs per square inch of the balding area saw an increase to an average of 1,014 hairs per square inch after two years of finasteride. 

What is finasteride used for? 

Although we often think of finasteride as a hair loss drug, it was a treatment for BPH first. Today, it’s used just as commonly to treat hair loss as it is for BPH. Let’s look more closely at how finasteride helps with both of these conditions. 

Hair loss

Hair loss can happen for many reasons, including genetic, hormonal, autoimmune, and nutrition-related causes. Androgenetic alopecia (AGA) is the most common cause of hair loss, occurring in up to 50% of biological men over 50 and up to 38% of biological women over 70. 

Finasteride treats hair loss by lowering how much testosterone converts into DHT, thereby decreasing the body’s levels of DHT. One study showed finasteride was 93% more effective than placebo at preventing further hair loss. Another study showed improvement in new hair growth in 48% of participants in the first year and 66% in the second year. 

While finasteride works on its own, it’s even more effective at treating hair loss when combined with minoxidil (brand name Rogaine), an over-the-counter topical treatment that goes directly on the scalp. 

BPH

Finasteride has been approved to treat benign prostatic hyperplasia (BPH) since 1992. BPH is a condition in which the prostate is enlarged, most commonly in biological men over the age of 50. This often causes difficulty with urination. 

Just like how finasteride works for hair loss, finasteride treats BPH by lowering DHT levels in the blood and prostate by preventing testosterone from converting into DHT. When levels of DHT in the prostate are lowered, the size of the prostate can be reduced, in some cases by up to 19%. 

The dose of finasteride is higher for treating BPH than it is for treating hair loss. The higher dose version is sold under the brand name Proscar. 

Other uses

Finasteride is only FDA-approved for hair loss and BPH, but it’s sometimes prescribed off-label in women with hirsutism (unwanted hair growth caused by high levels of androgen hormones). 

Because finasteride lowers androgen hormones such as DHT, there is some hope that the medication might also be useful in combination with estrogen therapy to provide gender-affirming care to transgender women. Unfortunately, as of now, there is not enough research to support finasteride for this use.

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Side effects of finasteride

Finasteride might be sounding pretty good right about now—and it is! It’s an effective treatment for many patients to stop hair loss and increase hair count. For patients with BPH, it relieves symptoms by decreasing the size of the prostate. 

However, no medication is without risk, including finasteride. 

Potential side effects of finasteride that tend to be of most concern are sexual side effects, including erectile dysfunction, low libido, and premature ejaculation. Many patients are so distressed about these potential side effects that they decide to forego treatment. 

For patients taking finasteride for hair loss, clinical trials showed sexual dysfunction from finasteride is unlikely to happen because the dose is quite low. Unfortunately, patients taking finasteride for BPH are at an increased risk of developing sexual side effects, particularly erectile dysfunction. This is likely because of the much higher doses needed to treat BPH. 

Other serious side effects of finasteride are unlikely but possible. These include: 

These are just some of the possible side effects of finasteride, so be sure to speak with your healthcare provider if you notice any other persistent changes while on this medication. 

While finasteride is effective and well-tolerated by most patients for both hair loss and BPH, it’s important to speak with your healthcare provider about any concerns you may have. Your complete medical history will help your healthcare provider make informed decisions about whether finasteride is right for you and which dosage is most appropriate.

Disclaimer

If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

References

  1. Adil, A. & Godwin, M. (2017). The effectiveness of treatments for androgenetic alopecia: A systematic review and meta-analysis. Journal of the American Academy of Dermatology, 77(1), 136–141.e5. doi: 10.1016/j.jaad.2017.02.054. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28396101/ 
  2. Chen, L., Zhang, J., Wang, L., et al. (2020). The Efficacy and Safety of Finasteride Combined with Topical Minoxidil for Androgenetic Alopecia: A Systematic Review and Meta-analysis. Aesthetic Plastic Surgery, 44(3), 962–970. Doi: 10.1007/s00266-020-01621-5. Retrieved from https://pubmed.ncbi.nlm.nih.gov/32166351/ 
  3. Fertig, R. M., Gamret, A. C., Darwin, E., & Gaudi, S. (2017). Sexual side effects of 5-α-reductase inhibitors finasteride and dutasteride: A comprehensive review. Dermatology Online Journal, 23(11). Retrieved from https://escholarship.org/uc/item/24k8q743
  4. Prescribers’ Digital Reference. (2023). Finasteride — drug summary. Retrieved Dec. 9, 2020 from https://www.pdr.net/drug-summary/Propecia-finasteride-378.609
  5. Kaufman, K. D., Rotonda, J., Shah, A., & Meehan, A. G. (2008). Long-term treatment with finasteride 1 mg decreases the likelihood of developing further visible hair loss in men with androgenetic alopecia (male pattern hair loss). European Journal of Dermatology, 18(4), 400–406. doi: 10.1684/ejd.2008.0436. Retrieved from https://pubmed.ncbi.nlm.nih.gov/18573712/ 
  6. Mcclellan, K. J. & Markham, A. (1999). Finasteride: a review of its use in male pattern hair loss. Drugs, 57(1), 111–126. doi: 10.2165/00003495-199957010-00014. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/9951956
  7. Phillips, T. G., Slomiany, W. P., & Allison, R. (2017). Hair Loss: Common Causes and Treatment. American Family Physician, 96(6), 371–378. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28925637/ 
  8. Smith, A. B. & Carson, C. C. (2009). Finasteride in the treatment of patients with benign prostatic hyperplasia: a review. Therapeutics and Clinical Risk Management, 5(3), 535–545. doi: 10.2147/tcrm.s6195. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710385/ 
  9. Varothai, S. & Bergfeld, W. F. (2014). Androgenetic alopecia: an evidence-based treatment update. American Journal of Clinical Dermatology, 15(3), 217–230. doi: 10.1007/s40257-014-0077-5. Retrieved from https://pubmed.ncbi.nlm.nih.gov/24848508/ 
  10. Zito, P. M., Bistas, K. G., & Syed, K. (2020). Finasteride. StatPearls. Retrieved from  https://www.ncbi.nlm.nih.gov/books/NBK513329/
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felix gussone
Felix Gussone, MD

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.

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Important Safety Information for Finasteride

Finasteride is for use by MEN ONLY and should NOT be used by women or children. 

Read this Patient Information before you start taking finasteride and each time you get a refill. There may be new information. This information does not take the place of talking with your healthcare provider about your medical condition or treatment. 

What is finasteride? Finasteride is a prescription medicine used for the treatment of male pattern hair loss (androgenetic alopecia). It is not known if finasteride works for a receding hairline on either side of and above your forehead (temporal area). Finasteride is not for use by women and children. 

Who should not take finasteride? 

Do not take finasteride if you: 

  • are pregnant or may become pregnant. Finasteride may harm your unborn baby. Females who are pregnant or who may become pregnant should not come in contact with broken or crushed finasteride tablets. If a pregnant woman comes in contact with crushed or broken finasteride tablets, wash the contact area right away with soap and water. If a woman who is pregnant comes into contact with the active ingredient in finasteride, a healthcare provider should be consulted. o If a woman who is pregnant with a male baby swallows or comes in contact with the medicine in finasteride, the male baby may be born with sex organs that are not normal. 
  • are allergic to any of the ingredients in finasteride. 

What should I tell my healthcare provider before taking finasteride? 

Before taking finasteride, tell your healthcare provider if you: 

  • have any other medical conditions, including problems with your prostate or liver 
  • Tell your healthcare provider about all the medicines you take, including prescription and nonprescription medicines, vitamins, and herbal supplements. Know the medicines you take. Keep a list of them to show your healthcare provider and pharmacist when you get a new medicine. 

How should I take finasteride? 

  • Take finasteride exactly as your healthcare provider tells you to take it. 
  • You may take finasteride with or without food. 
  • If you forget to take finasteride, do not take an extra tablet. Just take the next tablet as usual. 
  • Finasteride will not work faster or better if you take it more than once a day. 

What are the possible side effects of finasteride? 

  • decrease in your blood Prostate Specific Antigen (PSA) levels. Finasteride can affect a blood test called PSA (Prostate-Specific Antigen) for the screening of prostate cancer. If you have a PSA test done you should tell your healthcare provider that you are taking finasteride because finasteride decreases PSA levels. Changes in PSA levels will need to be evaluated by your healthcare provider. Any increase in follow-up PSA levels from their lowest point may signal the presence of prostate cancer and should be evaluated, even if the test results are still within the normal range for men not taking finasteride. You should also tell your healthcare provider if you have not been taking finasteride as prescribed because this may affect the PSA test results. For more information, talk to your healthcare provider. 
  • There may be an increased risk of a more serious form of prostate cancer in men taking finasteride at 5 times the dose of finasteride. 

The most common side effects of finasteride include: 

  • decrease in sex drive 
  • trouble getting or keeping an erection 
  • a decrease in the amount of semen 

The following have been reported in general use with finasteride: 

  • breast tenderness and enlargement. Tell your healthcare provider about any changes in your breasts such as lumps, pain or nipple discharge. 
  • depression; 
  • decrease in sex drive that continued after stopping the medication; 
  • allergic reactions including rash, itching, hives and swelling of the lips, tongue, throat, and face; 
  • problems with ejaculation that continued after stopping medication; 
  • testicular pain; 
  • difficulty in achieving an erection that continued after stopping the medication; 
  • male infertility and/or poor quality of semen. 
  • in rare cases, male breast cancer. Tell your healthcare provider if you have any side effect that bothers you or that does not go away. These are not all the possible side effects of finasteride. For more information, ask your healthcare provider or pharmacist. 

Keep finasteride and all medicines out of the reach of children. 

If you are experiencing a medical emergency, call 911 or seek immediate medical attention.

Withholding or providing inaccurate information about your health and medical history in order to obtain treatment may result in harm, including, in some cases, death.

You are encouraged to report negative side effects of prescription products to the FDA. Visit www.fda.gov/medwatch or call 1-800-FDA-1088.

Please see the full Prescribing Information for complete safety information.