Metformin's Surprising Skin Benefits Go Far Beyond Blood Sugar Control

Metformin has been a cornerstone of type 2 diabetes management for over six decades, but its pleiotropic biological actions are now drawing serious attention from dermatologists and longevity researchers. This 2025 narrative review from Democritus University of Thrace consolidates emerging clinical and mechanistic evidence for metformin's applications across a broad spectrum of skin disorders, suggesting the drug's dermatological story is only beginning to be written.

At the mechanistic core, metformin activates AMPK by inhibiting mitochondrial complex I, creating an energy-deficit state that suppresses mTOR signaling and gluconeogenesis while upregulating catabolic and anti-inflammatory pathways. Critically for skin health, it inhibits NFκB—a master regulator of inflammation—through both AMPK-dependent and independent routes, reducing TNFα, IL-1, IL-6, prostaglandin E2, and reactive oxygen species. It also lowers androgens by reducing both ovarian and adrenal output, and suppresses IGF-1 signaling, two key drivers of sebaceous gland hyperactivity and skin inflammation.

For acne, multiple small trials in women with PCOS and metabolic syndrome showed significant reductions in acne severity. One 8-week study of 40 patients with PCOS reported an 86% improvement in acne severity scores. A 6-month RCT found that low-dose pioglitazone-flutamide-metformin combination outperformed ethinyl estradiol-cyproterone acetate for acne scores. For acanthosis nigricans—a skin condition directly tied to insulin resistance—a double-blind RCT showed metformin 500mg BID produced significant improvement in neck lesion severity and texture within 4 weeks. In hidradenitis suppurativa (HS), a retrospective review of 53 patients treated with metformin for an average of 11.3 months showed clinical benefit, and case reports documented dramatic remission in patients with comorbid prediabetes and PCOS.

Beyond inflammatory conditions, the review highlights metformin's potential in wound healing—particularly relevant for diabetic foot ulcers—through promotion of angiogenesis, collagen synthesis, and autophagy-mediated cellular repair. Its anti-aging skin effects appear linked to activation of sirtuins, inhibition of the mTOR/S6K1 senescence pathway, and reduction of advanced glycation end products (AGEs) that stiffen dermal collagen. Evidence also points to potential benefit in psoriasis and rosacea through immune modulation and vascular effects respectively.

Importantly, the review also notes rare adverse cutaneous reactions attributed to metformin itself, including leukocytoclastic vasculitis, psoriasiform drug eruptions, lichen planus, and acute alopecia—underscoring that its dermatological profile is not uniformly beneficial and requires clinical vigilance.