Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 6/21/2022
Finasteride, the active ingredient in Propecia®, is an oral medication that’s designed to treat and prevent male pattern baldness. It was approved by the FDA to treat benign prostatic hyperplasia in 1992, and as a treatment for male pattern baldness in 1997.
Along with minoxidil, it’s one of two evidence-backed medications proven to help you keep and maintain your hair. In some cases, using finasteride could also help you regrow hair in areas of your scalp that have been affected by hair loss.
If you’ve searched online for information about finasteride, you might have noticed that it’s sold in two different dosage forms: finasteride 1mg and finasteride 5mg.
Although these two medications contain the same active ingredient, they’re designed for slightly different purposes.
Below, we’ve explained what finasteride is, as well as how it works as a treatment for hair loss in men.
We’ve also covered the main differences between the 1mg and 5mg finasteride tablets that are available, along with information on which option is best for you.
Before we get into the specifics of finasteride 1mg and 5mg, it’s important to quickly go over the basics of how and why hair loss occurs in men, as well as how finasteride fits in as a medication for treating hair loss.
Although hair loss can occur for a variety of reasons, most hair loss that affects men is the result of male pattern baldness, or androgenetic alopecia.
Contrary to many popular hair loss myths, male pattern baldness doesn’t develop from wearing a hat or washing your hair too frequently. Instead, it’s caused by long-term damage to your hair follicles caused by the androgen hormone dihydrotestosterone (DHT).
DHT, which your body produces as a byproduct of testosterone, plays an important role in your early development as a man. When you’re young, it’s responsible for your genital development, as well as the growth of your facial and body hair.
As you enter adulthood, DHT doesn’t play such a major role in your physiology. It can, however, bind to receptors in your scalp and cause your hair follicles to undergo a process referred to as miniaturization, in which hair growth slows and eventually stops.
Not everyone is equally affected by DHT, which is why some men develop hair loss earlier than others. Research suggests that men affected by hair loss tend to produce more DHT than their peers -- a factor that likely plays a role in the severity of male pattern baldness.
Interestingly, DHT is also responsible for other male health problems during adulthood, such as benign prostatic hyperplasia (BPH, or enlarged prostate).
BPH is relatively common, particularly in middle-aged and older men. According to the National Institutes of Health, BPH affects approximately 50 percent of men aged between 51 and 60 and as much as 90 percent of men aged 80 and older.
We’ve discussed the effects of DHT in more detail in our full guide to DHT and male pattern hair loss.
So, how does finasteride fit into this? Finasteride is part of a class of medications referred to as 5-alpha reductase inhibitors, or 5AR inhibitors. These medications work -- as you’d expect from their name -- by inhibiting the effects of an enzyme called 5-alpha reductase.
5-alpha reductase is the enzyme that’s responsible for converting testosterone into DHT within your body. By blocking the effects of 5-alpha reductase, finasteride helps to reduce DHT levels and slow down, stop or reverse the effects of male pattern baldness.
When it’s taken regularly, finasteride is very effective at blocking DHT. In fact, research shows that a normal dose of finasteride reduces DHT levels in your blood by as much as 70 percent, and by as much as 90 percent in your prostate gland.
Because male pattern baldness is such a widespread condition, several studies have looked into the effectiveness of finasteride as a treatment.
The results are generally overwhelming, showing that finasteride produces real improvements when it comes to stimulating hair growth and preventing hair loss caused by the effects of DHT from becoming more severe.
In a series of trials published in the Journal of the American Academy of Dermatology in 1998, researchers compared placebo to a non-therapeutic placebo to assess how well it worked as a treatment for male pattern baldness.
They found that balding men who took finasteride over the course of two years had significant increases in hair growth, with an average increase in hair count of more than 15 percent in the vertex scalp (crown) area.
A more recent study published in the journal Dermatologic Therapy found that 80.5 percent of men with male pattern baldness who used finasteride for 12 months showed improvements in hair growth.
Put simply, finasteride works, with numerous large-scale studies showing a slowing of hair loss and, for many men, improvements in hair growth.
Finasteride is most commonly used for hair loss at a daily dosage of 1mg. The vast majority of hair loss medications containing finasteride use this dose, including the original 1mg Propecia tablets.
Almost all studies of finasteride for hair loss use this dosage. For example, a study published in the journal Dermatology in 2004 involved the use of 1mg finasteride for 12 months to treat male pattern hair loss, with 80 percent of men showing improvements.
There’s no need to take more than 1mg of finasteride per day. Using a higher dose of finasteride won’t provide any improvements in your results, although it may increase your risk of developing side effects.
If you have benign prostatic hyperplasia (BPH) and you’re prescribed finasteride as a treatment, you’ll likely receive the 5mg dose of the medication.
This dosage of finasteride is often sold under the brand name Proscar®. It’s used specifically to control the growth of the prostate and reduce the severity of BPH symptoms. This dosage of finasteride is not used to treat hair loss.
Finasteride 1mg and finasteride 5mg both contain the same active ingredient, although they’re intended for different purposes.
The first is formulated to treat hair loss caused by DHT, while the second is formulated to treat benign prostatic hyperplasia (BPH).
If you’re prescribed finasteride, make sure you only take the medication at the dose prescribed to you by your healthcare provider.
Using a higher or lower dose of finasteride than prescribed may affect your results and increase your risk of experiencing side effects.
Serious side effects from finasteride are highly uncommon. However, like with other prescription drugs, a small percentage of men who use finasteride do report issues.
Potential side effects of finasteride 1mg include:
Decreased sex drive
Erectile dysfunction (ED)
Decreased ejaculate volume
These side effects are generally uncommon. For example, decreased libido -- the most common side effect of finasteride -- only affects 1.8 percent of men who take this medication at a dose of 1mg per day.
In comparison, clinical trials of finasteride 5mg found that 8.1 percent of men experience erectile dysfunction, with 6.4 percent of men reporting a reduced level of interest in sex and 3.7 percent reporting decrease ejaculation volume.
Additional adverse effects reported by men who use finasteride 5mg include rash, enlargement of the breast tissue and breast tenderness. Finasteride is not linked to any clinically significant drug interactions.
Although finasteride is associated with a reduced overall risk of prostate cancer, some scientific research suggests that it may contribute to an increased rate of high-grade prostate cancer.
These findings are likely the result of confounding factors and detection bias, and there’s a high level of agreement within the scientific community that finasteride is safe for most men to use as a treatment for hair loss.
Our full guide to the side effects of finasteride goes into more detail about these issues, as well as the steps that you can take if you experience side effects while using finasteride.
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In addition to finasteride, there are several other options that you may want to consider if you’re starting to lose your hair. These include over-the-counter medications like minoxidil and surgical procedures, such as hair transplant surgery.
Minoxidil is a topical medication for hair loss. Unlike finasteride, which works by reducing levels of DHT, minoxidil works by moving your hair follicles into the anagen, or active growth, phase of the hair growth cycle. It also stimulates blood flow to your scalp.
Research shows that minoxidil is effective at increasing hair growth, particularly when it’s used at the same time as finasteride.
For example, a study published in the journal Dermatologic Therapy found that 80.5 percent of men with male pattern baldness showed improvements after using finasteride for 12 months. It also found that 59 percent of men showed improvements while using minoxidil.
In comparison, more than 94 percent of participants in the same study who used finasteride and minoxidil showed improvements.
Many shampoos contain DHT blockers -- ingredients that may help to reduce DHT levels when applied topically. Common ingredients in hair loss prevention shampoos include the antifungal medication ketoconazole and Serenoa repens, or saw palmetto.
While the evidence for these ingredients isn’t quite as strong as it is for finasteride or minoxidil, some research does suggest that these ingredients may offer benefits for hair growth.
Our Hair Thickening Shampoo features saw palmetto to help target DHT while providing extra volume and moisture.
Finally, if you have more advanced hair loss -- or simply prefer a more permanent solution for male pattern baldness -- you may want to consider hair transplant surgery.
Hair transplant surgery involves extracting hair follicles from the back and sides of your scalp, which are resistant to the effects of DHT, then moving these follicles to areas with visible hair loss, such as your hairline and crown.
Undergoing a hair transplant can give you permanent results, but it isn’t cheap. The procedure can cost several thousand dollars (or more than $10,000 for a larger transplant) and requires a recovery period of approximately two to three weeks.
Our guide to hair transplants goes into more detail about the costs and potential benefits of hair transplant surgery.
Finasteride is available as a 1mg or 5mg tablet. If you have male pattern baldness, you should only take finasteride at a dosage of 1mg per day.
Taking finasteride at a higher dosage won’t do anything to reduce the severity of your hair loss, improve hair growth or speed up your results. However, it may increase your risk of developing side effects.
You can also learn more about your options for maintaining a healthy, thick head of hair in our guide to what you should take for hair loss.
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