Finasteride side effects

Finasteride intolerance is not common, but you should be familiar with some potential side effects.


What is Finasteride Used For?

Finasteride (Proscar, Propecia) is an antiandrogen and prescription drug that is used to treat pattern hair loss (androgenic alopecia) in men and enlarged prostate (benign prostatic hyperplasia) by constraining testosterone conversion into Dihydrotestosterone (DHT). Its use against male balding aims to reduce the rate of hair loss and regenerate hair growth on the frontal and mid-scalp parts. Finasteride is also used as a prostate cancer prevention medication. The drug further can be used against excessive female hair growth, such as facial hirsutism, and for supplementing hormone replacement therapy in transgender females.

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Proscar and Propecia are the established branded versions of Finasteride, both produced by Merck & Co., but various generic versions are widely available. The chief difference between Proscar and Propecia are different dosages (5mg vs. 1mg per tablet). Both are taken orally.

Depending on its use, the severity of the targeted condition and observed speed of improvement, different dosages of Finasteride and treatment durations are recommended.  

  • To reduce male pattern hair loss, the clinical recommended dose and treatment period will vary from patient to patient. However, adults are generally prescribed a dose of 1mg once a day. Long-term daily use for more than two years is not uncommon because it takes time for hair to grow back. 
  • For enlarged prostate (benign prostatic hyperplasia), adults usually are recommended to take 5mg once a day. The treatment period typically is long-term as instructed and monitored by your healthcare professional.
  • In prostate cancer prevention the dosage for adult men typically is 5mg once per day.
  • To suppress excessive hair growth in women, in particular male-pattern hair growth in the face (facial hirsutism), the dosage normally is decided case by case, but it does not exceed 5mg one day. For this purpose Finasteride is also available as a topical cream that can be directly applied to the skin.

It is best to follow your doctor’s guidance on when and how to take Finasteride.


Finasteride side effects

Finasteride is generally safe, but patients may experience some or all of the following mild side effects:

  • Dizziness
  • Mild disorientation
  • Swollen face and limbs
  • Skin rash and tingling sensation
  • Unusual weight changes
  • Abdominal aches
  • Breast tenderness


Finasteride sexual side effects

More severe side effects of Finasteride are rare, but for a small percentage of patients there can be sexual side effects during treatment and for several months after treatment has stopped. Seek medical advice in case you notice any of the following symptoms:

  • Impotence
  • Erectile dysfunction
  • Ejaculation disorder
  • Reduced libido
  • Loss of sexual desire
  • Reduced sperm volume


Several long-term studies of both Proscar and Propecia of up to seven years indicate that Finasteride is generally well tolerated, with the single most common side effects being temporary erectile dysfunction and loss of sexual interest. However, only some men are affected in this way and research shows that if these effects occur, they tend to be most severe during the initial phase of the treatment, with their intensity gradually decreasing later in the treatment. Moreover, two to four months after the medication is discontinued, in almost all afflicted patients any sexual side effects will be fully reversed.

A Finasteride treatment can be stopped at any time and at the earliest sign of sexual side effects. Although Finasteride’s long and proven track record of success in reversing male hair loss, it is recommended that you speak to your doctor to find out whether Finasteride is the right drug for you. As no contraindications have been observed between Finasteride and Viagra, the latter can be used to offset some of the above-discussed sexual side effects.  


Finasteride side effects on prostate cancer

Long-term use of finasteride may raise the risk of rare aggressive forms of prostate cancer. But the evidence is conflicting. One landmark long-term study (1993-2000) by the U.S. National Cancer Institute (NCI) with nearly 20,000 men showed Finasteride significantly decreased the general risk of prostate cancer by 25%, but at the same time could raise the risk of rare aggressive cancer types. 

However, recent research which followed up on the participants of the original NCI study and was published in 2019 could not find any notable difference in the prostate cancer mortality of the Finasteride and the placebo groups. Further clinical trials are needed before a final conclusion can be reached on whether Finasteride indeed raises the risks of rare aggressive prostate cancers.


Other side effects and contraindications

For adults there is no risk of overdose. Finasteride was studied in one-off doses of up to 400 mg and continuous doses of up to 80 mg per day for three months, without observing any significant adverse effects beyond the above-mentioned possible side effects.

Finasteride may cause birth defects in newborns and pregnant women are thus advised by the FDA to not take any Finasteride a few months prior or during the entire duration of their pregnancy.

If you have a chronic liver disease, do not take Finasteride.

Though there are no known major interactions with other drugs, consult your doctor before using finasteride.  



  1. Eur J Dermatol (2002). Long-term (5-year) multinational experience with finasteride 1 mg in the treatment of men with androgenetic alopecia. <SUBTITLE>Finasteride Male Pattern Hair Loss Study Group  </SUBTITLE>.
  2. James Tacklind et al (2010). Finasteride for benign prostatic hyperplasia. Cochrane Database of Systematic Reviews. Retrieved November 17, 2019, from
  3. Meena K. Singh, & Marc Avram (2014). Persistent sexual dysfunction and depression in finasteride users for male pattern hair loss. <SUBTITLE>A Serious Concern or Red Herring?</SUBTITLE>. The Journal of Clinical and Aesthetic Dermatology, 2014 Dec; 7(12): 51–55. PMCID: PMC4285451
  4. Phyllis J. Goodman, & Catherine M. Tangen et al (2019). Long-Term Effects of Finasteride on Prostate Cancer Mortality. The New England Journal of Medicine, 380:393-394. doi:
  5. Drug interactions between finasteride and viagra. (2019). Retrieved November 15, 2019, from website:

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