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Last updated October 15, 2019. 4 minute read

Does finasteride have side effects? What are they?

Finasteride is effective against male pattern hair loss, but as with many drugs, side effects have been reported. Those side effects are rare and can relate to sexual function, including ejaculation disorders and erectile dysfunction.

Self Written by Michael Martin
Reviewed by Mike Bohl, MD, MPH

As a wise TV theme-song author once opined, you take the good; you take the bad. The oral medication finasteride (brand name Propecia) is the most effective drug developed to date for treating male pattern baldness. In one European study, it was shown to be 93% effective in stopping hair loss (Kaufman, 2008). But like many drugs, finasteride can cause side effects, most commonly involving sexual function. Understandably, this can cause some guys who are considering finasteride a bit of anxiety. Some wonder if they should take the drug at all.

Let’s take a look at the facts. Then we’ll outline a few things to think about when you’re deciding whether to take finasteride for your hair loss.


  • Finasteride is effective against male pattern hair loss, but as with many drugs, side effects have been reported.
  • Those side effects involve sexual function, including ejaculation disorders and erectile dysfunction.
  • Decades of research have found that side effects are rare.
  • But they do happen, so you should consider that possibility when deciding whether to take finasteride.

How does finasteride work?

Finasteride is an oral medication known as a 5-alpha-reductase inhibitor. Approved by the FDA for hair loss in 1997, it works by stopping the production of DHT (dihydrotestosterone), a male sex hormone that can attack follicles on the head. Over time, DHT causes the follicles to shrink (a process called follicular miniaturization), so they produce thinner hairs and eventually none at all. 

What are the most common side effects of finasteride?

  • A decreased sex drive
  • Trouble getting or keeping an erection
  • A decrease in the amount of semen produced


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How common are finasteride side effects?

Not very. In clinical trials of Propecia, side effects were reported in 3.8% of men taking finasteride versus 2.1% of men taking a placebo (Mcclellan, 1999). 

Research showed that side effects stopped once men quit taking the drug, and the incidence of side effects declined with time, dropping to less than 0.3% in the fifth year of taking finasteride (Mysore, 2012).

In a 2017 meta-analysis published in Dermatology Online Journal, researchers reviewed 17 studies involving nearly 18,000 men who were taking 5-alpha-reductase inhibitors (Fertig, 2017). They found that in men that were taking 5-alpha-reductase inhibitors for hair loss, there wasn’t a statistically significant increase in sexual side effects when compared with placebo. Only in patients taking 5-alpha-reductase inhibitors for enlarged prostates (which requires a higher dose) were there significant increases in sexual side effects. 

Some men take a variation of finasteride called Proscar for a condition called benign prostatic hyperplasia (BPH). Its dose is five times higher than the common dose of finasteride for hair loss. There may be a higher risk of sexual side effects with the higher dose of finasteride. There may be an increased risk of a more serious form of prostate cancer (known as high-grade prostate cancer) in men who take Proscar. For more information, talk to your healthcare provider. 

Sounds pretty straightforward, right? Side effects are rare, transient, and reversible. 

But they do happen. And “rare” is pretty meaningless if it happens to you. It’s important to think about what it would mean if you’re one of those few men who have an issue. A tiny decrease in semen volume may be trivial, but erectile dysfunction may not be, even if it goes away with time. And in rare cases, some men have reported side effects that last after they stop finasteride. 

Studies have shown that finasteride used for hair loss is not associated with a statistically significant increase in sexual side effects. However, despite these study results, some men may still feel like they are affected. For those men, it is important to do a cost-benefit analysis. If you find your hair loss really bothersome, and you aren’t too worried about a small percentage risk of sexual side effects, getting a finasteride prescription might be the right choice for you. Conversely, if you’re on the fence about your hair loss and/or are a type that prefers to eliminate risk whenever you can, no matter how small, you might choose to skip it.

So think about it. But maybe not too long. No pressure, but there’s another fact you should know: Once DHT has caused a follicle to “die,” it’s difficult to revive it. The sooner you take action, the more likely you’ll be successful at reversing baldness and regrowing some hair. 

What are the other side effects of finasteride?

Finasteride can affect a blood test called PSA (prostate-specific antigen), which is used in screening for prostate cancer. An elevated PSA number might be a sign of the disease, and finasteride decreases PSA levels. If you have a PSA test done, tell your healthcare provider you’re taking finasteride; they’ll need to evaluate any changes in your PSA levels. You should also tell your healthcare provider if you haven’t been taking finasteride as prescribed because this may affect PSA test results too. You can learn more about PSA levels here.

These side effects have also been reported with finasteride:

  • Breast enlargement and tenderness. Tell your healthcare provider about any changes in your breasts such as lumps, pain, or nipple discharge.
  • Depression and suicidal thoughts
  • A 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 the 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.

Some other important things to keep in mind with finasteride: People with poor liver function should consult with their doctor before starting finasteride. Women who are pregnant or may become pregnant should not handle broken or crushed finasteride tablets; the active ingredient may be absorbed by the skin and cause birth defects in male babies. Remember to keep finasteride and all medicines out of the reach of children. Don’t use finasteride for a condition for which it was not prescribed. And don’t give finasteride to other people, even if they have the same symptoms you have.