FAQs About the Side Effects of Finasteride
Understanding all the adverse effects that finasteride may cause is part of the journey to treat hair loss or gradual thinning. We have compiled common patient questions with our answers on the topic.
Finasteride Side Effects
Finasteride is typically well-tolerated by men for treating hair loss, though extreme caution is advised for women. A wide-reaching review of research has highlighted underestimated finasteride side effects, specifically mental and sexual health risks.
Read on for insights from the office of Dr Bonaros, a leading healthcare provider in hair restoration. We look at the side effects of taking finasteride for hair loss, including a perceived link to prostate cancer and reactions in pregnant women.
Reviewed by Dr Epameinondas Bonaros
Table of Contents
Overview of Finasteride
Like minoxidil, another hair loss medication, finasteride’s hair growth effect was a secondary reaction to treating another condition.
The US Food and Drug Administration (FDA) approved finasteride (5 mg a day) as a treatment for benign prostatic hyperplasia (BPH) caused by an enlarged prostate in 1992. In the late 1990s, the FDA approved its use for male pattern hair loss.
Finasteride treats BPH under the brand name Proscar, while the medicine is marketed as Propecia to treat androgenetic alopecia. Note that the medicine would take a few months to work effectively.
Mechanism of Action
Finasteride’s mechanism of action for men involves inhibiting the enzyme 5-alpha reductase, which converts testosterone into dihydrotestosterone (DHT). This reduction in dihydrotestosterone levels helps address male pattern hair loss (androgenetic alopecia) in men with a genetic predisposition to the disorder.
The exact mechanism behind finasteride’s effects on women is not well understood. A 2020 review exploring finasteride as a potential treatment for female pattern hair loss suggests that it might promote hair growth in women by boosting insulin-like growth factor-1 (IGF-1) levels. Additionally, it highlights the possibility that finasteride may enhance hair density by reactivating dormant hair follicles in female patients.
Available Forms
The alpha-blocker is available in finasteride tablets and topical formulations. As a safety measure, finasteride tablets have a film coating to prevent accidental absorption through the skin. Topical solutions include a spray and gel.
Side Effects of Finasteride
Before starting finasteride, your healthcare professional should brief you on the potential unwanted effects,
particularly in the context of your medical history.
Listed Side Effects of Oral Finasteride Tablets
Depression, defined as a feeling of severe sadness and unworthiness, is a noted side effect of taking 1 mg of finasteride tablets. Below, you can explore more adverse reactions written up in the patient information leaflet.
These are uncommon sexual side effects mentioned in the information leaflet and may affect approximately 1 in 100 users. Symptoms include:
- Decreased libido
- Decreased ejaculation (this does not necessarily affect sexual function)
- Erectile dysfunction
Male infertility and/or low quality of semen is a lesser-known factor but included in the leaflet. Other side effects with an unknown frequency include:
- Anxiety
- Breast swelling or tenderness
- Haematospermia (blood in semen)
- Heart palpitations
- Impact on liver function (making the treatment unsuitable for individuals with liver disease)
- Pain in the testicles
- Suicidal ideation (suicidal thoughts)
Changes in breast tissue in men and women, such as, but not limited to, lumps, pain, enlargement or nipple discharge, should be immediately checked by a doctor. These symptoms could indicate serious conditions, such as breast cancer.
If you experience any of these or other symptoms while taking finasteride for hair loss, it will help to note what happened, when it started and how long it lasted. Detailed information will help your doctor prescribe the correct remedy and evaluate whether you need to discontinue your dose.
Allergy to Ingredients
The active ingredient in Propecia and its generic derivatives is 1 mg of finasteride. The other ingredients are cellulose, docusate sodium, lactose monohydrate, magnesium stearate, microcrystalline cellulose, sodium starch glycolate, and starch pregelatinised (maize starch).
The tablet coating is made from hydroxypropyl cellulose, hypromellose, red iron oxide (E172), talc, titanium dioxide (E171) and yellow iron oxide (E172)
Here are the symptoms of a serious allergic reaction:
- Breathing difficulties
- Difficulty swallowing
- Hives (skin rash)
- Swollen face, lips, tongue, or throat
Finasteride Side Effects in Men
All the side effects mentioned in the sections above apply to men.
Prostate Cancer
Long touted as one of the serious side effects of finasteride, studies have primarily ruled out the risk of prostate cancer. In actuality, the Prostate Cancer Prevention Trial (PCPT) published in 2003 proved that the medication can help prevent prostate cancer to a degree.
PCPT tracked 18,882 male patients taking finasteride for seven years to find a reduced prostate cancer risk of 25%. However, it appeared to increase the risk of high-grade prostate cancer. Later analyses showed that finasteride improves prostate cancer detection and grading accuracy during biopsies.
However, the product leaflet warns that 1 mg of finasteride, or Propecia, can influence a prostate-specific antigen (PSA) blood test. Therefore, it is vital to inform your doctor before starting your regimen.
Finasteride Side Effects in Women
The potential adverse outcomes of finasteride in women are so extreme that it is only used to treat hair loss under extreme circumstances, under the supervision of a healthcare professional.
The research on finasteride for women is limited, making it harder to determine the frequency of side effects.
However, the manufacturer provides a clear warning against pregnant women coming into contact with finasteride, as it could affect the sex organs of the fetus. Even contact with crushed finasteride tablets can have detrimental effects on pregnant women, as the medication can be absorbed through the skin.
Some of the known women-specific complications include:
- Acne
- Dizziness
- Folliculitis (inflamed hair follicles)
- Headaches
- Increased body hair growth
- Irregular menstruation
Finasteride Topical Side Effects
Generally, topical finasteride side effects are less severe than capsules but follow a similar trend. Two randomised controlled trials tested the efficacy of topical finasteride against the oral treatment as a control.
With a test group of 32 men, the overall finding was that certain doses of the solution are potentially minimising the negative sexual side effects of the capsule.
These are the potential side effects identified:
- Contact dermatitis
- Headaches
- Increased liver enzymes
- Nocturnal enuresis
- Oropharyngeal pain
- Presyncope
- Skin erythema
- Testicular pain
Finasteride Long-Term Side Effects
The product leaflet lists the following persistent sexual side effects after a patient stops taking finasteride:
- Difficulty having an erection
- Decrease in sex drive
- Problems with ejaculation
These symptoms, along with limited cases of breast cancer in men, are recognised as potential long-term side effects by the scientific community and manufacturers.
Post-Finasteride Syndrome
The somewhat controversial post-finasteride syndrome (PFS) refers to a so-called set of long-term symptoms experienced by men who had taken 5 alpha-reductase inhibitors.
Here are the symptoms used to diagnose PFS:
- Anxiety
- Brain fog
- Decreased libido
- Depression
- Erectile dysfunction
- Ejaculatory dysfunction
- Insomnia
- Panic attacks
- Suicidal thoughts
Finasteride Safety Review: Warning of Serious Side Effects
The Medicines and Healthcare Products Regulatory Agency (MHRA), the UK’s medicines regulator, completed a safety review of finasteride in 2024. Patient reports in safety databases prompted the review, which raised concerns about healthcare providers’ and patients’ lack of awareness of the medicine’s adverse effects.
In April 2024, the MHRA released their findings from analysing 25 articles and studies, product information and patient testimonials. The Safety Review of Finasteride: Public Assessment Report focused on two main areas:
- Psychiatric side effects
- Persistent sexual dysfunction risks
Studies on finasteride’s psychological effects show mixed but concerning results. Extensive studies involving hundreds of thousands of patients found that finasteride users have a higher chance of experiencing psychiatric issues compared to non-users, with a hazard ratio (HR) ranging between 1.22 and 1.61%.
Read MoreThe MHRA report found that finasteride may cause sexual side effects more frequently than previously understood. While taking the medication for hair loss, men have about 1.6 times higher risk of sexual problems compared to those not taking it.
Read MoreExperience science and sophistication in hair restoration.
Chat with us on WhatsApp for prescription information on finasteride and more innovative hair loss medication.
Do finasteride side effects go away?
The side effects generally subside when patients stop taking finasteride. There are, however, some instances of long-term adverse symptoms.
What should I do about a missed dose of finasteride?
If you accidentally skip your finasteride dose, do not take a double dose. Continue your schedule as usual. If you miss multiple doses, it could affect the efficacy of the treatment, and you will need to discuss the plan forward with your doctor.
Besides finasteride, what other medicines are used to treat hair loss?
Finasteride is not your only medicinal option to treat and manage hair loss. At Dr Bonaros’ clinic, we also use the following prescription medication in treatment plans:
- Minoxidil: Minoxidil is the first approved treatment for male-pattern hair loss, and it is also safe for women. While the topical solution is FDA-approved, the oral treatment is used off-label but is very effective, particularly for individuals who have experienced an allergic reaction to solutions.
- Dutasteride: Like finasteride, dutasteride blocks the development of 5-alpha reductase. It is used off-label but is considered one of the best medications for male pattern hair loss.
How can I reduce the side effects of finasteride?
While the reactions are rare, it helps to know how to reduce the side effects of finasteride. Only use the dose prescribed by your doctor, and don’t double the dose. If you experience side effects, discuss adjusting your dosage with your healthcare provider.
If you provide a complete medical history at your consultation, the chances of unwanted reactions will be drastically lower. Also, give accurate information about current medications, including herbal products, vitamins and other supplements.
Anecdotal evidence suggests that taking finasteride with a meal can reduce some common side effects. While no clinical evidence supports this, food does not interfere with the medication’s absorption, so it won’t hurt either way.
And remember, always take your dose at the same time every day.
Regain your self-confidence with finasteride. Get in touch with us via info@drbonaros.com
for further information on its side effects or other concerns.
Dr Bonaros: Personalised Hair-Loss Treatment Plans
Transform your look and regain your confidence with the high-quality hair restoration services at the Dr Bonaros hair transplant clinic. Our industry-recognised facility endeavours to provide honest, responsible and ethical advice tailored to each patient.
Leading our team, Dr Bonaros’ distinctive membership in both the British Association of Hair Restoration Surgery and the International Society of Hair Restoration Surgery reflects our clinic’s dedication to excellence. His natural fascination with emerging technologies — from artificial intelligence to robotics — drives our continuous evolution in restoration techniques.
In addition to closely monitored prescription finasteride protocols, we provide a range of other therapies, like our two-day full-head hair transplant procedure. By combining two treatments, such as the:
We can perform a safe and effective full hair transplant.
We understand your concerns about the side effects of finasteride. Book a consultation with Dr Bonaros to discuss your unique situation.
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