Hair loss in women is common, underdiagnosed, and undertreated. In clinical practice, it's one of the conditions where patients have often spent years trying over-the-counter treatments with minimal success before seeing a physician. That's partly because the underlying causes are diverse — and the treatment depends entirely on getting the diagnosis right.

The Most Common Causes

Female Androgenetic Alopecia (FAGA)

The most common cause of hair loss in women. Also called female pattern hair loss (FPHL). Unlike men, women rarely lose their frontal hairline — instead, FAGA presents as diffuse thinning over the crown and central part ("Christmas tree pattern"), with preservation of the frontal hairline. It's driven by androgen sensitivity in hair follicles, not necessarily elevated androgens (most women with FAGA have normal serum androgen levels).

Genetics play a major role. If your mother, maternal grandmother, or father had significant hair loss, your risk is higher. FAGA affects approximately 40% of women by age 50.

Telogen Effluvium

Diffuse shedding triggered by a physiological stressor 2–4 months prior. Common triggers include childbirth (postpartum telogen effluvium), severe illness, surgery, crash dieting, or significant psychological stress. The shedding is dramatic — patients often describe "handfuls in the shower" — but it's typically self-limited. Recovery takes 6–12 months once the trigger resolves.

Chronic telogen effluvium (lasting >6 months) is common in women of reproductive age and often has multiple overlapping triggers. It can be indistinguishable from FAGA clinically.

Thyroid Disease

Both hypothyroidism and hyperthyroidism cause hair loss. TSH testing is routine in any workup for women's hair loss. Hypothyroidism is particularly common in women and treatable — levothyroxine restores hair growth over 6–12 months once thyroid function normalizes. This is the most important secondary cause to exclude before attributing hair loss to androgenetic alopecia.

Iron Deficiency

Iron deficiency — even without frank anemia — has been associated with hair loss in women. Ferritin (stored iron) levels below 30–40 ng/mL may be sufficient to cause or worsen hair shedding in susceptible women. Women of reproductive age with heavy periods are particularly prone. Ferritin is an underordered test; serum iron alone isn't sufficient.

Polycystic Ovary Syndrome (PCOS)

PCOS affects 6–10% of women of reproductive age. Elevated androgens (testosterone, DHEA-S) associated with PCOS drive androgenetic alopecia and may also cause facial hirsutism. The workup for FAGA in premenopausal women includes androgen levels to screen for PCOS. Treatment targeting androgen excess (spironolactone, oral contraceptives) can meaningfully slow FAGA in this population.

Alopecia Areata

An autoimmune condition that causes patchy hair loss — classically round, well-defined patches anywhere on the scalp or body. It can progress to alopecia totalis (total scalp hair loss) or universalis (all body hair). Steroids have historically been first-line; JAK inhibitors (baricitinib, ritlecitinib) approved 2022–2023 represent a significant advance for moderate-severe disease. This is not androgenetic alopecia and doesn't respond to minoxidil or finasteride. Diagnosis requires clinical exam or biopsy.

Lab Workup

A standard physician workup for women's hair loss includes:

Biotin deficiency is almost never the cause of hair loss in well-nourished women — and high-dose biotin supplements interfere with thyroid and troponin lab assays, which is a patient safety concern.

Treatments With Real Evidence

Minoxidil (Topical and Oral)

The only FDA-approved topical medication for female pattern hair loss. Topical 2% and 5% minoxidil solutions and foam are available. The 5% formula is more effective; some women experience facial hair as a side effect at 5% (which resolves with discontinuation). Applied once or twice daily to the scalp.

Oral low-dose minoxidil (0.25–1.25 mg/day in women) has emerged as a highly effective option based on multiple retrospective and prospective studies. It avoids the scalp application issues of topical minoxidil and achieves better distribution to diffuse hair thinning. This is off-label but widely used by dermatologists and internists familiar with the literature. Contraindications include low blood pressure and heart conditions — physician evaluation required.

Spironolactone

An aldosterone antagonist with anti-androgenic properties. Used off-label for female pattern hair loss and PCOS-related hair loss. Typical dosing 50–200 mg daily. Reduces androgen effect on hair follicles. Not appropriate in pregnancy (teratogenic) — requires reliable contraception in women of reproductive age. Often combined with minoxidil for enhanced effect.

Finasteride in Women

Finasteride is FDA-approved for male pattern hair loss at 1 mg/day. In postmenopausal women, finasteride has shown benefit for FAGA in several RCTs and is used off-label. It is absolutely contraindicated in premenopausal women due to teratogenicity (can cause feminization of a male fetus). At YourMD, finasteride for women is only appropriate postmenopausal and with appropriate documentation.

Dutasteride

More potent 5-alpha reductase inhibitor than finasteride. Emerging evidence in women. Similar contraindication profile. Reserved for cases not responding to finasteride.

Platelet-Rich Plasma (PRP)

Injections of concentrated growth factors from the patient's own blood into the scalp. Growing evidence for FAGA; requires a series of in-person treatments. Not something YourMD prescribes (requires in-person procedure), but can be complementary to systemic therapy.

What YourMD Offers

Via telehealth: physician-supervised evaluation, lab ordering (ferritin, TSH, androgens), and prescription of topical minoxidil, oral minoxidil, or spironolactone with appropriate monitoring. Finasteride for postmenopausal women only. We do not treat alopecia areata via telehealth — that requires clinical examination, possibly biopsy, and often dermatology referral for JAK inhibitor therapy.

If you've been losing hair for more than 6 months without a diagnosis, the most useful first step is labs — not buying another bottle of biotin.