Introduction

Finasteride is one of the most commonly-prescribed medications for treatment of male pattern hair loss—also known as androgenic alopecia (AGA). But it’s also used as an off-label treatment for female pattern hair loss. Evidence suggests this medication can help regrow hair in both sexes.

But what’s the best dose of finasteride for women with AGA? Unfortunately, it’s complicated. This article sets out to evaluate the data, uncover the answers, and provide recommendations based on the current landscape of clinical research.

What Is Finasteride?

Finasteride is a drug developed to inhibit type II 5-alpha reductase. This is an enzyme in the body that converts free testosterone in dihydrotesterone (DHT).

Essentially, finasteride lowers DHT levels by reducing the amount of type II 5-alpha reductase circulating throughout our bodies. And by taking finasteride at 0.2 to 5.0 mg daily dosages, we can often reduce total DHT levels by 70%. ^[1]https://www.ncbi.nlm.nih.gov/books/NBK513329/

Why Use a Drug To Reduce DHT?

DHT is not just a metabolite of testosterone; it’s also the primary male hormone causally associated with androgenic alopecia.

We know this because studies have shown that men who cannot produce DHT are nearly fully-protected from going bald throughout a lifetime. Furthermore, clinical studies on DHT-lowering drugs – such as finasteride – show that if DHT levels are suppressed enough, 80-90% of men can arrest the progression of their pattern hair loss and even regrow 10-20% of their lost hair. ^[2]https://pubmed.ncbi.nlm.nih.gov/29407002/ ^[3]https://www.ncbi.nlm.nih.gov/books/NBK430924/

Similarly, studies on females with androgenic alopecia have shown that finasteride can also improve their hair loss outcomes. The evidence is less robust than for men, but finasteride is something many women should consider trying in order to improve their pattern hair loss.

Finasteride for Women: What’s the Perfect Dose?

In men, the FDA has approved the use of 1mg of finasteride for pattern hair loss. However, male and female hair loss cases are not always the same. Reducing DHT levels is often of therapeutic interest to fighting AGA – and for both sexes – but some clinical evidence suggests that females might need a different dose of finasteride versus males.

How Much DHT Does Finasteride Reduce?

Finasteride has what is known as a dose-dependent, logarithmic response curve for DHT reduction. In other words: a little bit of finasteride reduces nearly as much DHT as a lot of finasteride. For an example, see this chart:

Clinical studies have demonstrated that 0.2 mg and 5.0 mg reduce nearly the same amount of finasteride: 69% versus 72%, respectively.

Because of this, a lot of people actually prefer to use lower dosages of finasteride than what is generally prescribed. This practice is also supported by clinical data. For instance, in men, 0.2mg of finasteride AGA at a statistically similar level as 1.0 mg of finasteride over the course of a year. ^[4]https://europepmc.org/article/med/15319158

But is the same true with females? Unfortunately, the data is less clear.

Finasteride for Female Pattern Hair Loss: the Clinical Evidence

The FDA approves the use of 1 mg of finasteride for male pattern hair loss.^[5]https://www.fda.gov/drugs/information-drug-class/5-alpha-reductase-inhibitor-information But the underlying causes of male and female pattern hair loss cases (androgens such as DHT) are not always the same. Furthermore, while reducing DHT levels is of therapeutic relevance in treating AGA in men and women, some clinical evidence suggests that females might need a different dose of finasteride versus males. 

What does the available research tell us? Here are a few of the key studies on finasteride for women, and their main findings (summarized in the table below).

Finasteride for Women: Key Studies

Type of study	Number of patients	Patient condition	Finasteride dosage	Length of treatment	Assessment parameters	Outcomes	Reference
Double-blind, randomized control trial	67 treated, 70 placebo	AGA, post-menopausal, normal serum testosterone	1 mg, daily	12 months	Hair counts, photographic assessment, self-assessment, scalp biopsies	Serum DHT reduction but no effect on hair loss outcomes compared to placebo	[6]https://pubmed.ncbi.nlm.nih.gov/10674382/[7]https://pubmed.ncbi.nlm.nih.gov/11050579/
Randomized, unmasked trial	12 finasteride, 12 flutamide, 12 cyproterone acetate with estradiol, 12 no treatment	48 women, hyperandrogenic, age- and weight matched controls	5 mg, daily	12 months	Ludwig classification15 of female hair loss, self-assessment, and investigator assessment	No effect with finasteride	[8]https://pubmed.ncbi.nlm.nih.gov/11050579/
Single-blind, placebo-controlled trial	24 female patients included	AGA, age 23-38 years (mean 33)	1 ml topical application (0.005%), twice daily to affected area	16 months	Semi-quantitative investigator assessment, hair shedding quantification, self-assessment	Hair count and hair density improvements versus placebo (data not sex-stratified)	[9]https://www.tandfonline.com/doi/abs/10.3109/09546639709160517
Small trial	5 treated	Post-menopausal, normal androgen levels	2.5 or 5 mg, daily	18 months, review every 6 months	Self-assessment, investigator assessment, photographic assessment	Overall improvement	[10]https://pubmed.ncbi.nlm.nih.gov/15459533/
Small trial	10 treated	Post-menopausal	1 mg, daily	52-82 weeks	Self-assessment and photographic assessment	Overall improvement (9/10 patients)	[11]Ahn J, Cho SB, Kim MN, Ro BI. Finasteride treatment of female patterned hair loss in postmenopausal women. Korean J Dermatol. 2006;44:1094-1097.
Small trial	6 treated	AGA, age 30-76 years (mean 46.5), normal androgen levels	5 mg, daily	Weeks (not specified)	Retrospective questionnaire (self-assessment)	Overall improvement (5/6 patients)	[12]https://pubmed.ncbi.nlm.nih.gov/17454167/
Small trial	37 treated	Female pattern hair loss, pre-menopausal, age 19-50 years (mean, 33.7)	2.5 mg, daily (+ oral contraceptive drospirenone and ethinyl estradiol)	12 months	Self-assessment, photographic assessment, and hair-density scoring	Overall improvement by self-assessment (29/37), photographic improvement ((23/37), significant hair density improvement (12/37)	[13]https://pubmed.ncbi.nlm.nih.gov/16549704/
Small trial	41 treated	AGA, persistent adrenarche syndrome	2.5 mg, daily (+ ethinyl estradiol)	2 years	Not specified	Overall improvement	[14]https://pubmed.ncbi.nlm.nih.gov/19341939/
Small trial	4 treated	36, 40, 60, and 66 years old, elevated testosterone and hyperandrogenism	1.25 mg, daily	6 months to 2.5 years	Photographic assessment and self-assessment	Stabilization of hair loss within 6-12 months, hair growth improvements in 6 months – 2.5 years	[15]https://pubmed.ncbi.nlm.nih.gov/12399766/
Case study	1 treated	47-year-old, ‘male’ pattern hair loss, hysterectomy and ovariectomy, long-term hormone replacement	2.5 mg, daily (+continued testosterone supplementation)	10 months	Photographic assessment	Hair loss stabilization at 6 months, hair growth improvement at 10 months	[16]Hong JB, Chiu HC, Chan JY, Chen RJ, Lin SJ. A woman with iatrogenic androgenetic alopecia responding to finasteride. Br J Dermatol. 2007;156(4):754-755. doi:10.1111/j.1365-2133.2006.07719.x
Case study	1 treated	67-year-old, 18 month history of hair thinning, normal androgen levels	5 mg, weekly	12 months	Self-assessment and photographic assessment	Improvement, hair regrowth	[17]https://pubmed.ncbi.nlm.nih.gov/12366441/
Case study	1 treated	51-year-old, 8 month history of hair thinning, normal androgen levels	1 mg, daily	12-13 months	Hair density measurements	Hair density increased versus baseline	[18]https://pubmed.ncbi.nlm.nih.gov/15844649/

Finasteride for Women: Key Studies Takeaway

There is conflicting data regarding the efficacy of finasteride for female pattern hair loss. Some studies report improvements while others do not.

There are some key variables to consider when weighing the available evidence:

• The dose of finasteride used
• The length and frequency of treatment
• Oral administration versus a topical treatment
• Whether finasteride was used in conjunction with other drugs or therapies
• The type of hair loss in the patient groups (e.g., female pattern hair loss versus age-related thinning – and was this accurately determined?)
• Patient age, history, and status (e.g., pre-, or post-menopausal, or abnormal androgen levels)
• How the treatment was assessed (e.g., quantitative hair counting versus patient self-assessment)
• Whether the study contained appropriate controls (i.e., placebo-receiving patients, ideally matched for age, weight and medical history)
• The number of patients in the study (which affects the statistical power; was the study a case report of one patient, or a larger study with a control group?).

Interpreting research data can be difficult and confusing. such as different studies using different dosages of finasteride and for varying lengths of time, measuring different hair loss outcomes, and using different numbers and ages of patients.

The specific type of hair loss is also a crucial variable.^[19]https://pubmed.ncbi.nlm.nih.gov/30604525/  Often, studies reporting positive outcomes are based on patient self-reporting, which can be suspect and not meaningfully objective or quantitative in measuring true prevention or reversal of hair loss.

What is the best dose? Explaining the conflicting results.

Given the dose-response relationship between finasteride and DHT levels, shouldn’t 1 mg be as effective as 5 mg? Why aren’t women getting consistent regrowth across doses within these ranges?

Other discrepancies are the time for which finasteride was given. In men, 1 mg of finasteride can be effective in 6-12 months, but it is possible that women require more long-term treatment regimens.^[20]https://pubmed.ncbi.nlm.nih.gov/30604525/ Generally, success with finasteride in women has been reported in both the short- and long-term.^[21]https://pubmed.ncbi.nlm.nih.gov/12399766/

Alternatively, the difference in observed efficacies between studies may be due to patient background and the type of hair loss. Hair loss in patients suffering from PCOS or adrenarche (i.e., high levels of adrenal gland activity) likely has a clear causal link to abnormal androgen signaling (and therefore suitable for finasteride), where hair loss in post-menopausal women may be more akin to age-related hair ‘thinning’, and not linked to testosterone or DHT, which may explain why some studies find no effect with finasteride.^[22]https://pubmed.ncbi.nlm.nih.gov/10674382/^[23]https://pubmed.ncbi.nlm.nih.gov/11050579/^[24]https://pubmed.ncbi.nlm.nih.gov/12399766/

That said, finasteride is also reportedly effective in patients that are androgen-normal.20 Therefore, there needs to be more careful classification of the type of hair loss and the likely underlying mechanisms, as well as clear standardization of treatment outcome measurements. 

Conclusions

Does finasteride work for women suffering from hair loss? If so, what is the ideal dosage? 

Finasteride is most beneficial for women when their hair loss occurs alongside elevated androgen levels—much like hair loss in men.

It is likely that DHT is a major factor in a proportion of female hair loss cases. Finasteride is likely to be a beneficial part of a successful hair loss regimen in these cases. However, it is not clear that male and female pattern hair loss universally share the same underlying cause.

Finasteride may be less suitable in contexts of age-related hair thinning. Hair follicles are sensitive to all manner of different hormones and chemical signals, not just androgens such as testosterone and DHT.^[25]https://pubmed.ncbi.nlm.nih.gov/32731328/

The best dose is one that maximizes the desired benefits (prevention and reversion of hair loss) while minimizing any undesirable side effects.

Finasteride can be effective at reducing DHT even in small doses. Because of this, experimentation with low levels of finasteride may lead to results with far less exposure to chemicals. Topical treatments may also be considered to further reduce systemic side effects.

Therefore, the best dose will be patient-subjective. Prior consideration of your history, goals regarding hair loss, and experimentation with dosages is needed before you will find the ideal routine for your hair health.