What does finasteride do to the female body? Find out its side effects.

Finasteride is a drug approved for hair loss and prostate problems in men. It is not approved for hair loss in women anywhere, and any use in women is off-label and prescriber-led. This article summarises what the published studies report about it.

What is Female Pattern Hair Loss (FPHL)?

FPHL (Female Pattern Hair Loss) is a common condition that affects many women and is characterized by a gradual thinning of hair, usually at the top of the head, particularly along the parting line. Unlike male pattern baldness, which often results in receding hairlines or bald spots, FPHL leads to overall hair thinning. This condition is mainly linked to hormonal and genetic factors. One key cause is an imbalance in androgens (male hormones), which can lead to the miniaturization of hair follicles, making hair thinner and weaker. FPHL usually starts around the age of 40, although it can appear earlier due to factors like hormonal changes, stress, or genetics.

What is the difference between DHT and FPHL?

Dihydrotestosterone (DHT) is an androgen (male hormone) derived from testosterone. It plays a significant role in hair loss by shrinking hair follicles over time, making hair thinner and weaker. In men, high levels of DHT are strongly linked to male pattern baldness. In women, the relationship between DHT and hair loss is more complex. While some cases of FPHL involve increased DHT sensitivity, not all women with FPHL have high DHT levels. Instead, FPHL is often influenced by a combination of genetics, hormonal fluctuations, and aging. This difference is one reason why treatments like finasteride, which reduce DHT, do not translate straightforwardly from men to women.

Is finasteride effective for women?

Finasteride works by blocking an enzyme called 5-alpha reductase, which converts testosterone into a stronger form called dihydrotestosterone (DHT). In men, reducing DHT slows hair loss. In women the evidence is much weaker, and it depends on the dose.

The one large randomised trial is negative. Price and colleagues ran a one-year, double-blind, placebo-controlled, multicentre trial of finasteride 1 mg daily in 137 postmenopausal women aged 41 to 60 with androgenetic alopecia. After a year there was no significant difference in hair count between the finasteride and placebo groups, and the patient, investigator, photographic and scalp-biopsy assessments showed no improvement over placebo either [^2].

Later evidence comes from smaller, mostly uncontrolled studies at higher doses. A 2020 review by Iamsumang and colleagues gathered the published reports of finasteride in FPHL and found that the higher off-label doses used in practice, typically 2.5 to 5 mg daily, are where the reported hair-count improvements come from; the review describes finasteride as a possible option for selected patients — specifically postmenopausal women, or women of childbearing age who are using reliable contraception — under specialist supervision, while noting that the evidence base is small and largely uncontrolled [^1]. Finasteride is not FDA-approved for hair loss in women, and it is not approved for that use in the EU or UK either.

What are the risks and side effects of finasteride in women?

The 1 mg trial in postmenopausal women reported that finasteride was generally well tolerated at that dose [^2]. At the higher doses used off-label in FPHL, the reported adverse effects in the published case series and reviews include [^1]:

• Irregular menstrual cycles
• Decreased libido
• Fatigue
• Mood changes, including depression and anxiety
• Breast tenderness and other hormone-related complaints

These reports come mostly from small, uncontrolled studies, so they describe what patients reported rather than establishing how often each effect occurs. Anyone taking finasteride who develops mood changes, menstrual changes or breast symptoms should raise it with their prescriber rather than stopping or adjusting the dose alone.

Can finasteride cause problems during pregnancy?

This is the clearest and most serious risk. Finasteride blocks the conversion of testosterone to DHT, which is required for normal development of the external genitals in a male fetus. Because of this, women who are pregnant or may become pregnant must not take finasteride, and must not handle crushed or broken tablets — the drug can be absorbed through the skin. Intact, coated tablets are not a handling risk.

The FDA has classified finasteride as a Pregnancy Category X drug, meaning it is contraindicated in pregnancy because the risk clearly outweighs any benefit. This warning appears on the product labelling.

What the sources actually support

The honest summary is narrower than a simple yes or no.

• At 1 mg daily, the one properly controlled trial in postmenopausal women found no benefit over placebo [^2].
• At higher off-label doses, small and largely uncontrolled studies report improvement in some women, and the 2020 review treats it as a reasonable option for selected patients under specialist care [^1].
• It is contraindicated in pregnancy, and prescribers using it in women of childbearing age generally require reliable contraception [^1].
• Long-term safety data in women are limited.

Other options are commonly used for FPHL, including topical minoxidil (the only treatment with regulatory approval for women), low-level laser devices, platelet-rich plasma and prescribed anti-androgens. This article does not have the evidence in hand to rank those against finasteride, and which is appropriate depends on the individual.

Conclusion: Should women take finasteride?

That is a decision for a doctor, not for an article. What the published record shows is a negative randomised trial at 1 mg in postmenopausal women, some positive but weak evidence at higher off-label doses, an absolute contraindication in pregnancy, and no regulatory approval for this use anywhere.

Talk to a doctor or pharmacist before starting, stopping or combining finasteride. If you are pregnant, may become pregnant, or are breastfeeding, do not take finasteride and do not handle crushed or broken tablets.

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Sources:

1. Iamsumang, W., Leerunyakul, K., & Suchonwanit, P. (2020). Finasteride and its potential for the treatment of female pattern hair loss: Evidence to date. Drug Design, Development and Therapy, 14, 951-959. https://doi.org/10.2147/DDDT.S240615 (PubMed 32184564)

2. Price, V. H., Roberts, J. L., Hordinsky, M., Olsen, E. A., Savin, R., Bergfeld, W., Fiedler, V., Lucky, A., Whiting, D. A., Pappas, F., Culbertson, J., Kotey, P., Meehan, A., & Waldstreicher, J. (2000). Lack of efficacy of finasteride in postmenopausal women with androgenetic alopecia. Journal of the American Academy of Dermatology, 43(5 Pt 1), 768-776. (PubMed 11050579)