Metformin for Hidradenitis Suppurativa: Did Adding It to Doxycycline Help?

Adding metformin to doxycycline did not show added skin benefit in mild-to-moderate hidradenitis suppurativa (HS).¹

What was compared?

The double-blind Dutch trial randomized 62 adults to metformin, increased from 500 to 1,500 mg daily, or placebo. Both groups took doxycycline 100 mg daily for 24 weeks. Diabetes was excluded.¹²

How did skin severity change?

Primary outcome: change in IHS4, which counts nodules, abscesses and draining tunnels.¹³

Median improvement was three points with metformin versus two with placebo, alongside doxycycline in both groups. The between-group comparison was P = 0.596. This did not establish an added benefit or prove equivalence.¹

Five withdrawals before week six were excluded; the analysis included 29 versus 28 participants. Missing follow-up values used the last observation carried forward. ZonMw funded the study; authors declared no conflicts.¹

BMI, waist and fasting glucose favored metformin as secondary outcomes, without establishing added HS control.¹

How does this fit existing guidance?

The European S2k guideline, published online in December 2024, described metformin’s clinical evidence as inconclusive. Its discussion of possible benefits for insulin resistance and polycystic ovary syndrome predates this trial’s publication.³

Ask the prescriber which outcome is being targeted: fewer HS lesions, a metabolic condition, or both. Agree how each will be measured. The study regimen is a research detail, not a reason to extend an antibiotic prescription.

What needs checking before metformin?

The cited US label, revised October 2026, covers blood-sugar control in type 2 diabetes; HS use is off-label. Do not stop an existing prescription because its purpose differs from this trial’s question.⁴

Kidney function must be checked before starting. Metformin is contraindicated below eGFR 30 mL/min/1.73 m²; starting it at 30–45 is not recommended. Kidney monitoring continues during treatment.⁴

The boxed warning concerns lactic acidosis, a rare but potentially fatal emergency. The patient information says to stop the medicine and contact the clinician immediately for symptoms such as unusual muscle pain, trouble breathing or marked weakness. Review heavy alcohol use, liver or mitochondrial disease, interacting medicines, planned surgery and contrast imaging with the prescriber.⁴

The label calls for annual blood-count monitoring and vitamin B12 checks every two to three years. Discuss pregnancy plans too; metformin can restore ovulation in some premenopausal women who were not ovulating.⁴

“What to Say at the Appointment” in Skin, Head to Toe recommends bringing a written question, the products and medicines tried, and pregnancy plans. Put the treatment’s intended purpose at the top of that note, with the name of the clinician reviewing it.