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Is Finasteride Safe?
Dr. Michael May (FRCS)
Medically reviewed by
Dr. Michael May (FRCS)
Updated on March 26, 2024

Finasteride is the most commonly prescribed hair loss medication [1]. More than two-thirds of hair restoration clinics say they often prescribe this drug to their patients, so trichologists tend to agree that Finasteride is a safe medication.

Long-term large-scale studies suggest that Finasteride can be taken for months or even years without causing side effects for a significant number of patients [2-3]. However, prospective Finasteride users should know about its potential side effects, especially if they’re concerned about the safety of Finasteride. In this article, we’ll explore:

  • How safe Finasteride is
  • What Finasteride side effects can occur
  • How to decide if Finasteride is safe for you to take.
Table of Contents

How does Finasteride work for hair growth?

Finasteride is a DHT blocker. In individuals with male pattern baldness, dihydrotestosterone (DHT) binds to androgen receptors in the hair follicles which causes them to shrink. As the follicles shrink, they eventually stop producing hair, which in turn leads to hair loss.

Finasteride helps to reduce enzymes from converting testosterone to DHT. As a result, less DHT binds to the sensitive androgen receptors allowing the affected hair follicles to produce hair again.

How safe is Finasteride?

While there’s a lot of anecdotal and research-based evidence of side effects related to Finasteride, it’s important to note that these affect a very small proportion of people. According to one research report, Finasteride has a “well-established, excellent safety profile” [4].

In one 10-year study of 532 male Finasteride patients, researchers recorded mild, temporary side effects in 36 participants [3]. These included lower libido and erectile dysfunction. The effects were so mild that none of the affected patients stopped taking Finasteride.

Finasteride was originally developed to treat patients who are suffering from an enlarged prostate due to Benign Prostatic Hyperplasia (BPH). As well as treating hair loss, it’s still regularly prescribed to patients with BPH. So the prescription drug has gone through rigorous safety tests in order to be licensed as a drug for medical as well as cosmetic use.

Men who take Finasteride for BPH tend to take a higher dose (5mg a day) than those who use it to stop male pattern baldness (1mg a day). Research suggests even higher doses put men at only slightly higher risk of developing side effects [2].

Sexual side effects of Finasteride

Finasteride-related erectile dysfunction is arguably the drug’s most well-known side effect. Several patients have indeed reported sexual side effects when taking Finasteride. A 2011 campaign by the FDA in the US led to much greater awareness of Finasteride’s potential side effects [5].

However, more widespread knowledge doesn’t equate to more prevalence of these side effects. Multiple studies have found that Finasteride’s sexual side effects impact a very small proportion of users. One review of 73 research papers found that sexual dysfunction affects just 2.1% to 3.8% of patients taking Finasteride [6]. Erectile dysfunction was the most common sexual side effect, followed by ejaculatory dysfunction and lowered libido.

A comprehensive review found that when used in higher doses to treat benign prostatic hyperplasia (BPH), Finasteride was infrequently associated with ejaculation, erection, and libido problems [7]. However, it’s important to note that the dosage of Finasteride for BPH is typically around 5 times higher than the hair loss treatment dosage.

Another study found adverse sexual side effects in 1.2% to 1.8% of Finasteride users [4]. Side effects quickly resolved themselves among those who stopped taking the drug.

Finasteride has also been linked with a “nocebo” effect [8]. That means the patient’s negative expectations of the drug can trigger or worsen symptoms, rather than being caused solely by the drug itself.

Ultimately, there’s a very low chance you’ll experience erectile dysfunction and other persistent sexual side effects that may impede sexual function from using Finasteride [9]. Find out more about whether Finasteride side effects are permanent.

What impact does Finasteride have on fertility?

Finasteride affects your hormones, so it’s understandable to have concerns about whether Finasteride affects fertility, especially if you’re thinking of having a baby in the near future.

There’s a slight chance that Finasteride can decrease your sperm count [10]. When you stop taking the medication, sperm count usually returns to normal very quickly (although your hair loss may resume) [10-11].

Some research claims there are no apparent adverse links between Finasteride use and sperm production [12]. But in general, it’s a good idea to speak to your doctor or healthcare professional if you’re taking (or planning to take) Finasteride, and you and your partner are planning to try for a baby.

Propecia — the brand name for Finasteride — carries a warning against pregnant women handling Finasteride tablets due to potential complications with male foetuses [13]. This is one reason why Finasteride for women isn’t usually recommended.

While healthy babies have been born despite exposure to Finasteride, you should still be aware of the risks of Finasteride in pregnancy and take precautions where you can.

What effect does Finasteride have on mental health?

Recent research from 2020 has highlighted a potential link between Finasteride, suicidal thoughts, and other mental health concerns [14]. This seems to be particularly prevalent in men under 45 taking the drug to treat androgenetic alopecia (male pattern hair loss).

More research is needed to understand the link between mental health and Finasteride use. Researchers suggest it could be influenced by:

  • The impact of sexual side effects
  • Younger patients being more vulnerable to Finasteride’s adverse effects
  • A nocebo effect — including more reporting due to heightened awareness of the potential connection between Finasteride and mental health.

This research is in its infancy, but if you’re concerned about your mental health — regardless of whether you believe it could be linked to Finasteride use — it’s important that you get the right support. Your GP or health care professional can help you get the help you need.

Learn more about anxiety and hair loss.

Finasteride and male breast cancer

There are very rare instances of Finasteride use leading to gynecomastia and breast cancer in men. By 2010, 50 cases of male breast cancer had been linked to Proscar (Finasteride 5mg) use, and 3 cases had been linked to Propecia (Finasteride 1mg) [15]. More recent research from 2017 has also found an association between Finasteride use and male breast cancer [16].

It’s important to note that these numbers are extremely small compared with the number of Finasteride users. In 2013, more than 1.5 million patients took Finasteride in the United States alone [17]. So the proportion of Finasteride users who go on to develop breast cancer is very small.

However, if you experience symptoms including breast lumps, nipple discharge, or changes to your nipple, book an appointment with your doctor immediately, as these can be signs of breast cancer.

It’s also worth noting that the majority of Finasteride-linked male breast cancer cases are associated with the higher 5mg dose. Most people who take Finasteride to treat hair loss take the 1mg dose, further slashing your risk profile.

It should be noted that more recent evidence suggests there’s no correlation between Finasteride use and high-grade prostate cancer [21].

What is post-Finasteride syndrome?

Most patients stop experiencing side effects when they discontinue Finasteride [4, 6]. However, some report ongoing symptoms after they stop taking the drug. This is known as post-Finasteride syndrome (PFS) [9, 18].

Post-Finasteride syndrome is characterised by side effects including erectile dysfunction, low libido, depression and anxiety which linger after they stop taking the medication.

Limited research has been conducted into PFS. It’s only recently been recognised as a potential clinical problem, so more research is needed to establish the facts regarding PFS. However, some researchers note that, like with some other safety concerns related to Finasteride, the nocebo effect may affect a significant proportion of patients [19].

Finasteride drug interactions

According to the NHS, St John’s wort (an herbal remedy used to treat depression) may affect the effectiveness of Finasteride.

As always, it is recommended that you make sure to speak with your doctor or healthcare professional about drug interactions if you are taking any other prescription drugs, over-the-counter medicines, supplements, or herbal remedies in addition to Finasteride.

Allergic reactions

As with any medication, some individuals may experience hypersensitivity in the form of an allergic reaction. Allergic reactions to Finasteride are rare but are nonetheless, very serious. Seek medical care immediately if you experience any of the following symptoms of a serious allergic reaction which are as follows:

  • Swelling in the face, lips, tongue, or throat
  • Hives, rash, and/or itching skin
  • Difficulty breathing
  • Feeling dizzy, faint, or light-headed
  • Pain or tightness in chest
  • Rapid heart rate and/or palpitations

Should you take Finasteride?

Ultimately, it’s up to you whether you take Finasteride for hair loss and hair regrowth. Research shows Finasteride to be a safe, effective drug, though side effects can cause problems for a very small percentage of patients. Learn whether Finasteride works and how long Finasteride takes to slow hair loss

To put the risks in perspective, one large study of 3,177 patients found adverse reactions in 23 Finasteride users (0.7%) [20]. Of these, just 7 men stopped taking Finasteride after weighing up the benefits versus the risks.

If you’re worried about Finasteride safety, it’s worth consulting with your doctor before you start a course of Finasteride. This is particularly the case if you’re a man and:

  • Your partner is pregnant and/or breastfeeding
  • You’re planning to try for a baby soon
  • You have a history of mental health issues.

Otherwise, it’s entirely up to you. Side effects are rare — but only you can decide if the benefits outweigh the risks and if Finasteride is worth it.

What are some alternatives to Finasteride?

Finasteride results are excellent for hair loss patients as it can prevent the progression of hair loss in more than 95% of patients [20]. However, some men avoid taking Finasteride over safety concerns. In these cases, their hair loss often continues even after a hair transplant, leading them to need multiple hair transplants in future.

There are also alternatives to Finasteride you can take if you’re worried about Finasteride safety. See our comparisons of Finasteride vs Dutasteride and Finasteride vs Minoxidil to learn more.

If you’re considering using Finasteride to promote hair growth, speak to an impartial hair loss consultant to help you decide whether to take this hair loss drug. If you decide Finasteride isn’t for you, we can help you find the right treatment to restore your hair.

Book your free consultation at the Wimpole Clinic to get professional, impartial guidance on how to treat your hair loss.

Is Finasteride Safe?, Wimpole Clinic

  1. ISHRS Practice Census 2022
  2. Longitudinal analysis of sexual function reported by men in the Prostate Cancer Prevention Trial
  3. Long-term (10-year) efficacy of finasteride in 523 Japanese men with androgenetic alopecia
  4. Use of Finasteride in the Treatment of Men With Androgenetic Alopecia (Male Pattern Hair Loss)
  5. Global online interest in Finasteride sexual side effects
  6. Finasteride and sexual side effects
  7. Medical therapy for benign prostatic hyperplasia: sexual dysfunction and impact on quality of life
  8. Finasteride 5 mg and sexual side effects: how many of these are related to a nocebo phenomenon?
  9. Risk of erectile dysfunction associated with use of 5-α reductase inhibitors for benign prostatic hyperplasia or alopecia: population based studies using the Clinical Practice Research Datalink
  10. Finasteride use in the male infertility population: effects on semen and hormone parameters
  11. Finasteride-associated male infertility
  12. Effect of 1-mg Dose of Finasteride on Spermatogenesis and Pregnancy
  13. Propecia label | FDA
  14. Investigation of Suicidality and Psychological Adverse Events in Patients Treated With Finasteride
  15. MHRA: The risk of male breast cancer with Finasteride
  16. Finasteride treatment and male breast cancer: a register-based cohort study in four Nordic countries
  17. Finasteride | Drug Usage Statistics, United States, 2013 – 2020
  18. Post-Finasteride syndrome: An emerging clinical problem
  19. Post-Finasteride syndrome: a surmountable challenge for clinicians
  20. Evaluation of efficacy and safety of finasteride 1 mg in 3177 Japanese men with androgenetic alopecia
  21. Long-Term Effects of Finasteride on Prostate Cancer Mortality

Dr. Michael May (FRCS)
Medically reviewed by Dr. Michael May (FRCS)Updated on March 26, 2024
The Wimpole Clinic offers FUE Hair, Beard & Eyebrow Transplants & Trichology.
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