Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 6/15/2022
Finasteride, the active ingredient in Propecia®, is one of the most popular, effective medications for men looking to prevent hair loss. It’s also one of the treatments for male pattern baldness, or androgenetic alopecia, that’s approved by the FDA.
It’s easy to see why. Used on its own, finasteride has been shown to stop hair loss and improve hair growth in the majority of men, often within three to four months.
Finasteride comes in tablet form and is designed for use one time per day. It’s easy to use and, under the supervision of a healthcare professional, can stop male pattern baldness in its tracks without the need for costly cosmetic procedures.
But does finasteride come with a risk of side effects? The short answer is, well, yes. Like other medications, finasteride can cause side effects.
However, there’s a lot of misinformation about both finasteride and its potential side effects out there.
In general, the risk of side effects from finasteride is low. Research shows that the vast majority of men who use finasteride over the long term benefit from a successful hair loss treatment with few or no undesired results.
With this said, if you’re considering using finasteride, or if you’re already taking it, it’s important to understand what to expect.
Below, we’ve listed the common and uncommon side effects you may experience while taking finasteride to treat male pattern hair loss.
We’ve also talked about what you can do to reduce your risks of developing side effects while using finasteride.
Finasteride is a prescription drug that’s used to treat hair loss caused by male pattern baldness, or androgenetic alopecia. It comes in tablet form and belongs to a class of medications referred to as 5-alpha-reductase inhibitors, or 5ARIs.
To understand how finasteride works, it’s important to quickly go over the basics of how and why male pattern baldness develops.
Male pattern baldness is the most common form of hair loss that affects men. It’s responsible for the classic receding hairline that many guys develop in their 20s, 30s or 40s, as well as hair loss that can develop around the crown of the head.
Contrary to many popular hair loss myths, male pattern baldness doesn’t develop as a result of wearing a hat too tight or dealing with stress at work.
Instead, male pattern baldness develops gradually as a result of the effects of a hormone called dihydrotestosterone, or DHT, on your hair follicles.
DHT is a type of androgen hormone, or male sex hormone. Your body creates it as a byproduct of testosterone. In your early life, DHT plays a key role in your physical development, including the development of your male physical features.
As you get older, DHT is less important for your physical development. It can, however, attach to receptors in your scalp and cause your hair follicles to gradually miniaturize, resulting in reduced hair growth and the development of male pattern baldness.
DHT can also affect other areas of your body, including your prostate, where it’s responsible for a condition called benign prostatic hyperplasia (BPH, or enlarged prostate).
Finasteride works by inhibiting an enzyme called 5-alpha-reductase, which converts part of your body’s testosterone into DHT. On average, a normal dose of finasteride reduces DHT levels by as much as 70 percent.
This reduction in DHT levels protects your hair follicles from miniaturization, which can prevent male pattern baldness from becoming worse. It may also help to stimulate hair growth in areas of your scalp that have already been affected by DHT.
In the more than 20 years that finasteride has been used to treat hair loss, several studies have found that it’s very effective.
For example, a study published in the Journal of the American Academy of Dermatology found that men affected by male pattern hair loss showed significant improvements in hair count after using finasteride over a two-year period, all with minimal adverse events.
A newer study published in the journal Dermatologic Therapy found that more than 80 percent of men with pattern hair loss who used finasteride displayed improvements.
Like other FDA-approved medications, finasteride was put through a thorough testing process before it went on sale.
Because of this, lots of data is available about its potential side effects, as well as its risks and drug interactions.
When looking into the side effects of finasteride, it’s important to be aware that two versions of finasteride are available.
The first is Propecia, the form of finasteride that’s used to treat hair loss. This is available as a daily use finasteride tablet at a dosage of 1mg. This is the form of finasteride that you’ll get if you have male pattern baldness, or androgenetic alopecia.
Finasteride 1mg is sold under the brand name Propecia and as a generic medication. Both the brand name version of finasteride and the generic have the same effects on your hair.
The second is Proscar®, a high-strength version of finasteride that’s prescribed to treat benign prostatic hyperplasia. This medication contains 5mg of finasteride per tablet. Due to its higher dosage, it’s more likely to cause certain side effects.
Common side effects of 1mg finasteride include:
Erectile dysfunction (ED). In clinical trials, approximately 1.3 percent of men who took finasteride experienced erectile dysfunction, compared to 0.7 percent of men who used a non-therapeutic placebo.
Decreased libido. Approximately 1.8 percent of men who used finasteride 1mg reported a reduced level of interest in sex, compared to 1.3 percent of men who were treated with a non-therapeutic placebo.
Ejaculation disorder. In total, 1.2 percent of men who used finasteride reported issues related to ejaculation, with 0.8 percent reporting a lower semen volume. In comparison, 0.4 percent of men who used a placebo treatment reported lower semen volume.
Very few men who took finasteride in clinical trials experienced serious side effects. In fact, only 1.2 percent of men that participated in clinical trials of finasteride stopped using their medication because of adverse effects.
It’s worth noting that 0.9 percent of men who received a non-therapeutic placebo in clinical trials also discontinued treatment because of side effects, suggesting that the rate of severe adverse effects that are directly caused by finasteride is low.
As you’d expect, side effects are more common with the higher-dose 5mg version of finasteride that’s used to treat BPH, or prostate enlargement.
In one-year clinical trials of Proscar (finasteride 5mg), men who used finasteride at a daily dose of 5mg reported the following side effects:
Erectile dysfunction (ED). Erectile dysfunction was reported by 8.1 percent of men who used finasteride, compared to 3.7 percent of men who used a non-therapeutic placebo.
Decreased libido. A reduced level of interest in sex was reported by 3.7 percent of men who used finasteride, compared ot 3.4 percent of men who used a placebo.
Changes in ejaculation. Decreased ejaculation volume and ejaculation disorder were reported by 3.7 and 0.8 percent of men who used finasteride, compared to 0.8 and 0.1 percent of men who used a non-therapeutic placebo.
Breast enlargement and/or tenderness. Enlargement of breast tissue and tenderness of the breasts was reported by 0.5 percent and 0.4 percent of men who used finasteride, compared to 0.1 percent of men who used a non-therapeutic placebo.
Skin rash. 0.5 percent of men who received finasteride reported developing a skin rash, compared to 0.2 percent of men who used a non-therapeutic placebo.
Some of these side effects, such as sexual health issues, appear to become less common when finasteride is used over the course of several years.
Finasteride may also cause other, less common side effects. These include depression, pain in the testicles, breast tenderness, blood in semen, breast pain or nipple discharge.
These side effects occur in a small percentage of men who use finasteride. It’s important to tell your healthcare provider if you develop side effects that are persistent or severe after you start using finasteride.
Some ingredients in finasteride may cause an allergic reaction in some people. Potential signs of an allergic reaction include rash, hives, itching and swelling that affects the tongue, lips, face and throat.
Inform your healthcare provider as soon as possible if you start to notice any signs of an allergic reaction after using finasteride.
Side effects are an unfortunate reality of almost all medications. However, using finasteride the right way may reduce your risk of developing side effects.
Try the the following tips and techniques to use finasteride safely:
Take finasteride at the correct dosage. Finasteride is prescribed at a dosage of 1mg per day to treat male pattern baldness. There’s no need to take a higher dose than this, as it won’t improve your results.
Using finasteride at a higher dosage may increase your risk of side effects. Stick to your recommended dosage and inform your healthcare provider if you develop any issues.
Try to take finasteride at around the same time each day. Finasteride typically works best when it’s taken at approximately the same time every day. You can use finasteride with or without food.
If you forget a dose, skip it and wait for the next one. If you forget to take finasteride, skip the missed dose and continue your regular dosing schedule the next day.
Do not take more than one dose of finasteride at a time. Taking more than one dose of finasteride, even if to make up for a missed dose, could increase your risk of developing side effects.
If you develop side effects, let your healthcare provider know. In certain cases, side effects are a temporary annoyance. Make sure to inform your healthcare provider so that they can track your progress and, if necessary, provide expert advice.
Tell your healthcare provider about other medications. Finasteride generally doesn’t cause interactions with other drugs. However, it’s still important to tell your healthcare provider about any other medications you use or medical conditions you may have.
Store finasteride properly. Finasteride should be stored at room temperature inside its original container. Avoid storing finasteride in the bathroom or other spaces with heat or excessive moisture.
Consider taking finasteride at a lower dosage. If you experience severe or persistent side effects after starting finasteride, your healthcare provider may recommend reducing your dosage.
Another way to potentially reduce your risk of side effects is to switch to topical finasteride -- a form of finasteride that you can apply directly to your scalp.
Like oral finasteride, topical finasteride works by reducing levels of DHT. However, it does so at a scalp level, meaning there’s less of a systematic effect of DHT levels in your bloodstream and throughout your body.
Several recent studies, including one study published in the Journal of the European Academy of Dermatology and Venereology, have found that topical finasteride is also effective at treating hair loss, all with a reduced likelihood of adverse reactions.
We offer topical finasteride in our Topical Finasteride & Minoxidil Spray, which can be applied directly to your scalp to promote hair growth and prevent hair loss from worsening.
If you search online for information about finasteride, you may come across headlines claiming that taking finasteride will give you irreversible erectile dysfunction, kill your libido for good and cause other permanent sexual side effects.
While it’s true that finasteride can cause sexual side effects, these headlines don’t really tell the full story.
In 2012, the FDA issued a warning stating that finasteride can increase a person’s risk of facing sexual side effects, including a libido, ejaculation and orgasm disorders.
Sexual dysfunction, generally in the form of erectile dysfunction, decreased libido and reduced ejaculate volume, has been experienced by men taking finasteride. This is what prompted the FDA in 2012 to call attention to the matter.
But the FDA also noted that these side effects have a low incidence rate. Only a tiny percentage of men who use finasteride report experiencing any sexual side effects.
For some of these men, the sexual side of finasteride effects persisted even after they stopped using this type of medication. Most of the time, though, the side effects stopped when treatment stopped.
Even though the risk of experiencing sexual side effects is small, it’s normal and understandable to be concerned about this potential risk.
If you’re considering using finasteride, make sure to let your healthcare provider know about any of your concerns before you start using this medication.
They’ll be able to put these risks into context and provide more information about what you can expect after starting finasteride.
If you are one of these rare cases of recurring sexual side effects, it’s important to talk with your healthcare provider to find out about your options.
“I tried several different options before but Hims combined approach of all four methods by far created the best results.”
“Hims has been the greatest confidence boost, no more bald jokes! I look and feel so much younger!”
“When I show my barber my progress, he is always in disbelief. I have to recommend Hims to any guy who’s experiencing thinning.”
“Cost effective and affordable. My hair keeps growing thicker, fuller, and at a fast rate.”
“I noticed a huge change in the overall health and fullness of my hairline.”
“Now after 5 months I’m able to style waves first time in 10 years!”
“I decided to jump right in and I'm so glad I did. I definitely feel ten years younger!”
“In just as little over two and half months, I can really see the difference in thickness and in color.”
“4-months strong and my confidence boosted back up to 100% using Hims, future me really does thank me.”
“I’m a 34 year old father of two and have been using Hims for over a year now. My hair is back to what it was in my mid twenties.”
Finasteride is a safe and well-tolerated medication that’s used by millions of men worldwide, all without any significant problems.
However, one point of contention among experts is whether or not long-term use of finasteride carries the potential for prostate cancer risks or benefits.
Perhaps the most commonly referenced research on the topic, the Prostate Cancer Prevention Trial (PCPT), was a study funded by the National Cancer Institute (NCI) in 1993 specifically to explore the potential link between finasteride and prostate cancer.
The study was carried out over seven years and included nearly 19,000 men who used either finasteride or a placebo daily.
The findings of the study, published in 2003, found that the men in the finasteride group were nearly 30 percent less likely to get prostate cancer than men in the control group.
However, the study also concluded that men who took finasteride 5mg were at greater risk of developing a form of high-grade prostate cancer (high-grade cancer cells are more abnormal under a microscope and tend to spread throughout the body faster).
This finding prompted the FDA to release a safety announcement regarding 5-alpha reductase inhibitors (including finasteride), noting the potential for an increased risk of high grade prostate cancer. This original study tied up the score and it’s been this way for quite some time.
The most recent development in this line of research came in 2019, when researchers found no increase in the number of men who had passed away due to prostate cancer between the group that used finasteride and a control group.
So, after more than 20 years of follow up research, there is no measurable difference in prostate cancer mortality between the groups.
Experts have said that this data goes a long way to alleviate concerns, but given the very small number of men with lethal prostate cancer in both study arms, it’s likely that this will continue to be an area of ongoing research.
In trials of finasteride, a very small percentage of men developed male breast cancer. However, several cases also occurred in placebo-treated men. It’s unclear if finasteride played any part in the development of male breast neoplasia.
In conclusion, the interplay of finasteride and cancer continues to evolve. If you’re considering taking finasteride daily to help with your hair loss, make sure to discuss the potential risks with your healthcare provider.
Finasteride is a safe and effective medication that’s used by millions of men worldwide to slow down, prevent and reverse the effects of male pattern baldness.
Although finasteride can cause side effects, research shows that these only happen in a small percentage of men who use this medication, especially at the low 1mg per day dosage used to treat male pattern baldness.
Of these side effects, the most common are erectile dysfunction, a reduced level of interest in sex and ejaculation issues.
Although other side effects can occur, they’re uncommon, and for most men, cease to occur if treatment with finasteride is stopped.
While the side effects of finasteride may seem alarming at first, it’s important to keep them in context. The reason we know about these mild, uncommon side effects is that finasteride has been studied for decades and put through the most rigorous testing processes available.
The same can’t be said for the majority of unregulated hair loss treatments, including many of the over-the-counter supplements promoted as alternatives to finasteride.
If you’re starting to notice the early signs of hair loss and want to take action, taking finasteride can be an effective way to maintain the hair you have and stimulate growth in the areas of your scalp that are affected by male pattern baldness.
You can also view other options for protecting and restoring your hair in our complete range of hair loss treatments. If you’re interested in using finasteride, you can learn more about what to expect in our guide to the typical finasteride results timeline.