Spironolactone

What it is

Spironolactone is a potassium-sparing diuretic and aldosterone blocker that also has anti-androgen properties. Aldactone label

• Status: prescription-only everywhere we checked. In the US, Aldactone is approved for heart failure, add-on treatment of high blood pressure, oedema and primary hyperaldosteronism, not for hair. For women's pattern hair loss only topical minoxidil is FDA-approved, so spironolactone is off-label. Kearney 2026 We found no hair indication in the EU or UK either. Topical spironolactone is not a licensed product.

How it works

It competes with DHT and testosterone at the androgen receptor, so the follicle receives less of the signal that shrinks it. Abdel-Raouf 2021 Because women's pattern loss is only partly androgen-driven, responses vary, and in an 80-woman series no hormone level predicted who responded. Sinclair 2005 See DHT and pattern hair loss.

What the studies show

• Open series (80 women, at least 12 months, no placebo): 44% regrew hair, 44% stayed stable and 12% kept losing; spironolactone 200 mg and cyproterone acetate gave similar results. Sinclair 2005
• Add-on to minoxidil (120 premenopausal women, 24 weeks): spironolactone added density over minoxidil 5% alone (p = 0.009) but less than microneedling did, and most side effects were in the spironolactone arm. Liang 2022
• Placebo-controlled pilot (48 women, 24 weeks, all on minoxidil 3%): moderate-to-marked improvement in 38% vs 9% (p = 0.034); terminal hairs rose 9.5 vs 5.3/cm² (p = 0.063); menstrual irregularity affected 37.5%. Werachattawatchai 2025
• Versus finasteride 5 mg (60 women, with minoxidil 2%): the spironolactone combination was rated better at 4 months (excellent response 56.7% vs 0%). Sadeghzadeh Bazargan 2024
• Versus bicalutamide (204 women, 24 weeks): bicalutamide gave more hair-count gain (frontal +5.05 vs +3.13/cm²), but the authors found no significant clinical difference. Jha 2026 A 24-month retrospective cohort of 187 women found at least one grade of improvement in 54.4% on spironolactone vs 37.3% on bicalutamide (p = 0.030). Gil-Redondo 2026
• Low-dose pairing (100 women, 12 months, open label): oral minoxidil 0.25 mg plus spironolactone 25 mg cut the severity score by 1.3 points and the shedding score by 2.6, with no raised potassium. Sinclair 2018
• Pooled data: in a meta-analysis, 56.6% improved overall (65.8% in combinations vs 43.2% on its own), with high variability. Aleissa 2023
• What is missing: the 2016 Cochrane review found no trials of spironolactone and called for them. van Zuuren 2016 The only placebo-controlled trial since is the 48-woman pilot above, which is why the overall evidence is fairly good rather than strong.

How it's used in studies

• Oral, women: 100 mg daily in recent trials Werachattawatchai 2025; 200 mg in older series Sinclair 2005; 25 mg with low-dose oral minoxidil. Sinclair 2018 A systematic review found oral doses of 25 to 200 mg, mostly 80 to 110 mg, and better results in combination. Wang 2023 Doses above 100 mg did best in one retrospective cohort. Gil-Redondo 2026
• Combined with oral minoxidil: among 432 women, 37.7% reported an adverse effect, mainly extra facial hair (12.3%) and dizziness or light-headedness on standing (12.0%); other blood-pressure drugs raised the dizziness risk. Dewey 2026
• Topical: a 1% gel performed similarly to minoxidil 5% gel in 80 women Hassan 2025, but a 5% solution produced no trichoscopic change at 16 weeks in another small trial, where topical finasteride and minoxidil did better. Al Sayed 2025 Topical use has been proposed for men because it avoids feminising effects. Wang 2023
• Men, oral: not used. Gynecomastia is the label's most common adverse reaction, about 9% of men in a heart-failure trial and dose-related. Aldactone label

Side effects and safety

• Pregnancy: spironolactone may affect sexual development of a male fetus (feminisation in rat studies) and should be avoided in pregnancy, so women who could conceive need reliable contraception. Aldactone label
• Common effects: irregular periods, breast tenderness, dizziness, more urination and lower libido. Aldactone label
• Potassium: high potassium is a label warning, but in 974 healthy young women on spironolactone for acne the rate (0.72%) matched the background rate (0.76%), so routine checks were judged unnecessary in that group. Plovanich 2015 Older women, people with kidney disease, and those taking ACE inhibitors, ARBs or potassium supplements are a different risk group.
• Blood pressure: it lowers blood pressure, and dizziness is common alongside oral minoxidil. Dewey 2026
• Cancer: a meta-analysis of 7 studies (4.5 million people) found no link with breast cancer (relative risk 1.04) and lower prostate cancer risk. Bommareddy 2022 A UK cohort of women over 55 found no increase in breast cancer (hazard ratio 0.99). Mackenzie 2012 The current US label has no boxed warning. Aldactone label

Bottom line

Spironolactone probably helps a meaningful share of women with pattern thinning, usually as an add-on to minoxidil, and especially in women who also have acne, oily skin or excess facial hair. Confidence is moderate: the placebo-controlled data are small and short. It needs reliable contraception if pregnancy is possible, and oral use is not appropriate for men. The generic pill is cheap, the pairing with low-dose oral minoxidil is a common mid-range route, and bicalutamide is an alternative with its own liver-monitoring requirement (see bicalutamide). Discuss with a doctor.