Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 2/20/2023
If you’re a man looking to find practical treatment options for hair loss, you’ve no doubt heard of finasteride. In fact, that’s probably why you’re here.
Finasteride is the active ingredient Propecia® and is one of the most popular and effective hair loss medications available today. It’s also one of only two treatments for male pattern baldness approved by the FDA.
That’s because it works. Used on its own, finasteride has been shown to stop hair loss and even improve hair growth in the majority of men who use it, often within three to four months.
Finasteride comes in both oral and topical forms 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 or hair pieces.
However, like other medications, finasteride comes with its own risks.
There are also a lot of misleading finasteride warnings, which is why it's important to get the facts right before you start using it yourself.
In general, the risk of side effects from finasteride is low. Research shows 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.
Low libido, erectile dysfunction and ejaculation issues are a few of the known finasteride sexual side effects.
Some common ways to reduce finasteride side effects in men include following the prescribed dosage, taking the medicine at the same time every day, or taking a lower dosage.
If you’ve tried to reduce finasteride’s side effects and they persist, talk to your healthcare provider to learn about your other options.
Below, we’ve listed the common and uncommon side effects you may experience while taking finasteride to treat male pattern hair loss, as well as what you can do to reduce your risks of developing side effects while using finasteride.
Both topical and oral finasteride are prescription drugs that’re used to treat hair loss caused by male pattern baldness, or androgenetic alopecia. It belongs to a class of medications referred to as 5-alpha-reductase inhibitors, or 5ARIs.
Finasteride works by inhibiting an enzyme called 5-alpha-reductase, which converts part of your body’s testosterone into dihydrotestosterone, or DHT — the primary culprit behind male pattern baldness.
Male pattern baldness is the most common form of hair loss that affects men today. In fact, it's the type of hair loss that’s responsible for the classic receding hairline that many guys develop in their 20s, 30s and 40s, as well as balding that develops around the crown of the head.
This form of hair loss develops gradually due to the effects of DHT on the hair follicle. Review our complete guide on DHT and hair loss to learn more about this process.
This reduction in DHT levels protects your hair follicles from miniaturization, preventing male pattern baldness from becoming worse while stimulating re-growth in some patients.
The best part? These claims are backed by science.
For example, a 1998 study published in the Journal of the American Academy of Dermatology gave 1,553 men with male pattern hair loss daily oral finasteride over a two-year period and saw significant improvements in hair count.
A newer study from 2015 published in the journal Dermatologic Therapy found that 80 percent of the 450 men with pattern hair loss who used finasteride displayed improvements over the course of 12 months.
Like other FDA-approved medications, finasteride underwent a thorough testing process before it became available to the public.
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 and common finasteride warnings, it’s important to be aware that two versions of finasteride are available.
Propecia is the form of finasteride that’s used to treat hair loss. It’s available as a daily finasteride tablet at a 1mg dosage. Finasteride 1mg is what you’ll get if you have male pattern baldness, or androgenetic alopecia.
The second is Proscar®, a high-strength finasteride dosage that’s prescribed to treat benign prostatic hyperplasia (an enlarged prostate). This medication contains 5mg of finasteride per tablet. While both medications cause similar side effects, the higher dosage has additional warnings.
Common Propecia side effects (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 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 who participated in finasteride clinical trials 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 finasteride that’s used to treat BPH, or benign prostatic hyperplasia.
While the majority of the side effects overlap in these drugs, Proscar also causes a few unique side effects, including:
Breast enlargement and/or tenderness
In one-year clinical trials of Proscar (finasteride 5mg), men who used the drug at a daily dose of 5mg reported breast enlargement at a rate of 0.5 percent (compared to 0.1 percent in the placebo group), breast tenderness at a rate of 0.4 percent (compared to 0.1 percent in the placebo group and skin rash at a rate of 0.5 percent (compared to 0.2 percent in the placebo group).
Some of these side effects, such as sexual health issues, appear to become less common when finasteride is used over several years.
Finasteride may also cause other, less common side effects. These include:
Pain in the testicles
Blood in semen
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:
Itching and swelling that affects the tongue, lips, face and throat
Inform your healthcare provider immediately if you notice any signs of an allergic reaction after using finasteride.
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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 following tips and techniques to use finasteride safely:
Take finasteride at the prescribed 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.
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.
Store finasteride properly. Store finasteride at room temperature inside its original container. Avoid storing finasteride in the bathroom or other spaces with heat or excessive moisture.
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, alter your dosage.
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.
If you search online for information about finasteride, you may come across headlines claiming that taking it will give you erectile dysfunction, kill your libido and cause other — even permanent — sexual side effects.
Naturally, these bold claims would scare off anyone who values their sex life.
While sexual side effects aren't unheard of, you can rest easy knowing they’re rare and typically subside with cessation.
In 2012, the FDA issued a warning stating that finasteride can increase a person’s risk of facing sexual side effects, including 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 possible side effects have a low incidence rate. Only 3.8 percent of men who use finasteride report experiencing any sexual side effects.
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, let your healthcare provider know about any of your concerns before you start using it.
They’ll be able to put these risks into context and provide more information about what you can expect after starting finasteride.
There’s a reason finasteride has been used to treat male pattern hair loss for over 20 years — it actually works and it’s considered safe.
However, it's important to note that while long-term side effects are uncommon, they may occur in some users.
Today, researchers are finding that some individuals that have taken finasteride for hair loss continue to suffer from adverse side effects even after cessation. This condition is known as post-finasteride syndrome (PFS).
PFS is characterized by its persistent side effects on one’s sexual function and psychology that develop in users who have stopped using finasteride. Possible symptoms include:
Low sex drive
Difficulty in achieving orgasm
While most of this research is based on self-observations or online studies that cannot be fully corroborated, some national agencies are now requiring these products to include persistent side effects within their labels.
In a 2014 study published in the American Journal of Men’s Health, researchers reviewed 131 men with a mean age of 24 who had taken finasteride for hair loss treatment and reported symptoms while taking the medication.
The study discovered that men suffered from a number of sexual and psychological symptoms well after they stopped taking the medication, indicating that PFS may have been present.
While this pilot study showed that the participants had strong correlations to common PFS symptoms, the research cannot make a generalization and infer that finasteride directly causes these outlined symptoms above.
Put simply, more research is needed to form any definitive conclusions on the long-term effects of finasteride.
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 actually 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 be more aggressive).
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.
But opinions change as research develops. Remember when we used to think that you could just think positive thoughts if you had depression? Well, the same goes for finasteride.
The most recent development in this line of research came in 2019 when researchers found no increase in the number of prostate cancer deaths between the group that used finasteride and a control group — just under 10,000 men total.
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 regarding finasteride and prostate cancer, 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.
So, let’s talk brass tacks: are you more prone to developing cancer if you use finasteride over the long term? Most likely not. But that’s not to say it isn’t a topic researchers aren’t exploring, or one that people looking to use finasteride shouldn’t make themselves aware of.
As always, if you have any concerns whatsoever about the safety of finasteride, the best thing for you to do is talk to a healthcare professional. They’ll be able to outline everything you should know about one of the world’s most popular FDA-approved hair loss treatments.
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.
If you’re looking into treating hair loss with oral or topical finasteride, here’s what you should take away from this article:
Finasteride comes in oral and topical applications. Oral finasteride is FDA-approved for the treatment of hair loss. Topical finasteride is brand new to the market. While topical finasteride has proven effective and safe as the product has developed, it’s still waiting for an official nod from the FDA. Even so, as of now, side effects appear to be just as mild as its oral counterpart.
Finasteride is tried and true. 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.
Side effects are generally mild. Of the noted finasteride 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 when they stop taking 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.
We offer finasteride online, either by itself or with the topical hair loss treatment minoxidil in our Hair Power Pack.
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.