Side Effects of Finasteride for Hair Loss

young man looking into mirror examining his hairline for hair loss

Finasteride is an FDA-approved medication that was originally created to treat benign prostatic hyperplasia. Today, Finasteride is primarily used to treat male pattern hair loss. Finasteride is most commonly prescribed as an oral medication under the brand name Propecia, although it can also be used as a topical medication. In both cases, Finasteride is a type of hormone therapy and works by inhibiting the conversion of Testosterone into dihydrotestosterone (DHT). When testosterone is converted into DHT, it can cause the hair follicles to shrink, leading to thinning hair and eventually baldness.


While Propecia and other finasteride-based prescription medications can be an effective hair loss treatment, they also have a long list of harmful side effects. Some of the more serious side effects include sexual dysfunction, allergic reaction. Some studies even indicate that there may be a link between oral finasteride and and cancer in men.

How Does Finasteride Treat Hair Loss?

Finasteride is a type of 5-alpha reductase inhibitor. 5-alpha reductase is an enzyme that helps to convert testosterone into dihydrotestosterone (DHT). DHT is a hormone that is responsible for many developmental changes in the body during puberty, including the enlargement of the prostate gland. In men, DHT is also responsible for causing male pattern hair loss. By inhibiting the production of 5-alpha reductase, Finasteride decreases the amount of DHT in the body, which can help to prevent hair loss and promote hair growth.

Oral Finasteride (Propecia)

There are two ways in which Finasteride can be used to treat hair loss. It can either be taken orally in pill form, or it can be used topically. When taken orally, Finasteride is typically prescribed as Propecia. Propecia is a brand name for the oral medication that contains 1mg of Finasteride. For the treatment of thinning hair, men are typically prescribed to take one 1mg tablet of Propecia per day. It may take several months before results are seen, and the full effects of Finasteride may not be realized for up to a year.

Topical Finasteride

When used topically, Finasteride is sometimes combined with other medications, such as minoxidil. Minoxidil is a medication that is applied directly to the scalp in order to promote hair growth. It is available over-the-counter in a variety of products, such as Rogaine. Finasteride is typically used in a 2% concentration when combined with minoxidil. It is important to note that topical finasteride is not FDA-approved for the treatment of hair loss and should only be used under the supervision of a healthcare professional. Additionally, unlike topical Minoxidil, topical Finasteride can not be purchased over-the-counter, and acquiring it will require first obtaining a prescription from a licensed health care professional.

Finasteride for Benign Prostatic Hyperplasia

Finasteride was originally FDA-approved in 1992 for the treatment of benign prostatic hyperplasia (BPH), also known as enlarged prostate. BPH is a condition that affects many men as they age, and can cause urinary symptoms such as difficulty urinating and a need to urinate more frequently. Finasteride works to treat BPH by inhibiting the production of 5-alpha reductase, which decreases the amount of DHT in the body. By decreasing the amount of DHT, Finasteride can help to shrink the enlarged prostate gland – which can help improve urine flow.


Finasteride is typically prescribed in 5 mg tablets to treat BPH. These 5 mg tablets, often under the brand name Proscar, are much larger than the 1mg tablets of Propecia used by most men for thinning hair. It’s important that men do not attempt to use these larger 5 mg finasteride tablets for thinning hair without permission from their doctor or pharmacist. The common side effects associated with this medicine have pose an increased risk with the larger 5 mg dosage.

Propecia for Male Pattern Hair Loss

close up shot of man's receding hairline

The most common use for Finasteride is the treatment of male pattern baldness. Male pattern hair loss is a type of alopecia that occurs in men who are genetically predisposed to be sensitive to the effects of DHT. When exposed to DHT, these men may experience thinning hair, receding hairlines, and eventually complete baldness. Propecia is typically prescribed as a treatment for thinning hair in men because it can help to reduce the levels of DHT in the scalp, which can stop the progression of hair thinning and even promote new hair growth.

Finasteride for Female Pattern Hair Loss

young woman looking into mirror at her receding hairline

While Finasteride is FDA approved to treat androgenetic alopecia in men, it is currently not approved for women. There are some concerns that finasteride use in women can cause adverse events. There is particular concern that finasteride could cause birth defects if the medicine is given to pregnant women. However, there are some recent studies indicating that oral finasteride may be well tolerated by women with androgenetic alopecia. Although further studies are needed, women with female pattern hair loss may consider speaking with their doctor or pharmacist to see if this medication could be right for them.

Finasteride and Prostate Cancer

There has been some concern that Finasteride may increase the risk of developing prostate cancer. However, studies have shown that there is no increased risk of developing prostate cancer in men taking Finasteride for BPH or thinning hair. In fact, a 2020 review study showed that men who took Finasteride have a lower risk of developing prostate cancer than men who did not take the medication. This recent research has lead some to consider the use of finasteride as a preventative for men who are at risk of developing prostate cancer.

Common Side Effects of Finasteride

Finasteride has a long list of potential side effects, some of which can be quite serious. While not a complete list, here are some of the most commonly reported side effects:

Depression from Finasteride

A review study published in 2021 demonstrated a link between finasteride and depression in men. This link was shown to be independent from patient medical history and appears to demonstrate a clear link between oral finasteride and depression.

Sexual Side Effects

Finasteride may cause sexual side effects, such as erectile dysfunction and decreased libido. These side effects impacting sexual function are most common in men who take oral Finasteride (Propecia). It is important to note that most of these side effects are typically not permanent and usually resolve once the medication is stopped.

Decreased Libido from Finasteride

Finasteride may cause decreased libido (sex drive). When a man experiences decreased libido, he may notice a decreased interest in sex and a reduction in sexual urges. This decreased urge for sex can ultimately have a negative impact on a man’s relationships and sex life.

Erectile Dysfunction

man sits on edge of bed looking sad with his head in his hand as a woman is lying in the bed behind him

It’s been reported that 2-4% of men using finasteride tablets develop some form of erectile dysfunction (ED). When a man develops ED, he will have difficulty getting or maintaining an erection. This side effect is typically temporary and will resolve if the patient decides to stop taking finasteride tablets. However, some patients have reported persistent sexual side effects from finasteride.

Abnormal Ejaculation

Clinical studies have shown that men using finasteride have an increased risk of developing a range of possible side effects that impact sexual function. Abnormal ejaculation is one of the negative side effects linked to Finasteride. Specifically, finasteride use has been linked to decreased semen production and decreased ejaculatory volume. These serious side effects may potentially be related to the way finasteride interacts with the seminal vesicles – the part of male sexual anatomy responsible for sperm production.

Testicular Pain

Although not widely recognized as a common side effect, there have been some published reports of testicular tenderness reported by patients taking Finasteride. Some patients have even reported decreased testicular size.


Studies have linked prescription drugs containing finasteride with a condition called Gynecomastia – which is a condition in which men develop an increased amount of breast glad tissue. Early symptoms of this condition can include breast pain or tenderness. Eventually this condition can develop into visible breast swelling.

Male Breast Cancer

There have been some reports of male breast cancer occurring in men taking finasteride. While the link between finasteride and male breast cancer is not definitive, it is important to be aware of this potential side effect. If you experience any lumps or pain in your breasts, or nipple discharge, you should stop taking finasteride and call your doctor immediately.

Liver Disease

There have been some reports of serious liver injury in men taking finasteride. Although the link between finasteride and liver disease is disputed, this is one of the potential side effects of this medicine worth discussing. Patients with liver disease will sometimes develop jaundice (yellowing of the skin and eyes), dark urine, abdominal pain, and unexplained fatigue. If your finasteride treatment leads to any of these symptoms, it is important to stop taking the medicine and call your doctor right away.

Allergic Reaction

Some men taking finasteride may experience hypersensitivity reactions or allergic reactions, such as hives, skin rash, swelling, and trouble breathing. In rare cases, these reactions can be severe and require medical immediate attention. If you have difficulty breathing while taking finasteride, immediately discontinue use and seek emergency help.

Adverse Drug Interactions

When taking finasteride with other drugs there is always a possibility for adverse reactions. With adverse drug reactions, a potentially safe medicine can have unexpected side effects due to the influence of other prescription medicine. Before taking finasteride, make sure to tell your doctor if you are taking any other prescription or over the counter medicine. Your doctor should be familiar with the prescription label drug information on the other drugs and able to determine if there is a likeliness of adverse interactions with finasteride.

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