Does finasteride work?

Felix Gussone, MD - Contributor Avatar

Reviewed by Felix Gussone, MD, Ro, 

Written by Rachel Honeyman 

Felix Gussone, MD - Contributor Avatar

Reviewed by Felix Gussone, MD, Ro, 

Written by Rachel Honeyman 

last updated: Apr 14, 2023

4 min read

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, 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.  

Finasteride Important Safety Information: Read more about serious warnings and safety info.

Hair loss

More hair, less hassle. All from the comfort of home.

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. 


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.

Finasteride Important Safety Information: Read more about serious warnings and safety info.

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.


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.

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

April 14, 2023

Written by

Rachel Honeyman

Fact checked by

Felix Gussone, MD

About the medical reviewer

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