Is metformin (a biguanide oral hypoglycemic agent) effective in treating hidradenitis suppurativa?

Metformin for Hidradenitis Suppurativa

Metformin is a viable adjunctive treatment option for hidradenitis suppurativa, particularly in pediatric and adolescent patients with insulin resistance, though it is not included in standard first-line treatment algorithms for adults. 1

Guideline-Based Recommendations

The 2025 North American Clinical Practice Guidelines for special populations explicitly recommend metformin for pediatric patients with HS, especially in cases of insulin resistance. 1 This represents the most recent and highest-quality guideline evidence supporting metformin use in HS, though notably limited to the pediatric population with specific metabolic indications.

The 2019 North American guidelines for general HS management do not include metformin in their therapeutic algorithm or treatment recommendations, indicating it is not considered a standard therapy for the broader adult HS population. 1

Clinical Evidence and Efficacy

Response Rates and Outcomes

• A retrospective study of 53 HS patients treated with metformin showed subjective clinical response in 68% of patients, with 19% achieving quiescent disease on metformin monotherapy. 2
• The mean dose used was 1.5 g/day for an average duration of 11.3 months. 2
• Drug survival rates were 61% at 6 months and 39% at 12 months, indicating reasonable tolerability. 2

Safety Profile

• Metformin was well tolerated, with only 11% experiencing gastrointestinal side effects. 2
• No serious adverse effects were reported across multiple studies examining metformin for dermatological conditions. 3

Insulin Resistance Considerations

• Insulin resistance was present in 75% of HS patients in one cohort, though its presence did not predict clinical response to metformin. 2
• This finding suggests metformin may work through mechanisms beyond glucose metabolism in HS treatment. 2

Position in Treatment Algorithm

Metformin should be considered as an adjunctive therapy rather than monotherapy for HS. 3 It is not a replacement for established first-line treatments:

• Mild disease (Hurley I): Topical clindamycin 1% remains first-line; metformin can be added if metabolic comorbidities exist. 4
• Moderate disease (Hurley II): Clindamycin-rifampicin combination (71-93% response rate) is superior to metformin and should be prioritized. 4
• Severe disease (Hurley III): Adalimumab is the established first-line biologic; metformin serves only as adjunctive therapy. 4

Specific Patient Populations

Pediatric and Adolescent Patients

In pediatric patients with HS requiring anti-androgens, metformin is specifically suggested, especially in cases of insulin resistance. 1 This represents the strongest guideline-based recommendation for metformin use in HS.

Adults with Metabolic Comorbidities

• Given the strong association between HS and metabolic syndrome, obesity, and insulin resistance, metformin addresses both the skin disease and systemic comorbidities. 2
• Screening for cardiovascular risk factors (BP, lipids, HbA1c) is recommended in all HS patients, making metformin particularly logical when metabolic abnormalities are identified. 4

Practical Implementation

Dosing Strategy

• Start metformin at 500 mg daily with food to minimize GI side effects. 2
• Titrate to 1.5 g/day (500 mg three times daily or 750 mg twice daily) over 2-4 weeks. 2
• Assess response at 12 weeks using pain scores and inflammatory lesion counts. 4

When to Consider Metformin

• Pediatric/adolescent HS patients with documented insulin resistance. 1
• Adult HS patients with concurrent metabolic syndrome, prediabetes, or type 2 diabetes. 2
• As adjunctive therapy to antibiotics or biologics in patients with metabolic comorbidities. 3
• When cost or access limits availability of biologic therapies. 5

Critical Limitations and Pitfalls

Do not use metformin as monotherapy for moderate-to-severe HS (Hurley II-III). 3 While 19% achieved disease control with metformin alone, this was in a mixed-severity population and cannot replace proven therapies like clindamycin-rifampicin or adalimumab. 2

The absence of metformin from adult treatment algorithms in major guidelines reflects limited high-quality evidence. 1 The available data consists primarily of retrospective studies and case series rather than randomized controlled trials. 2, 3

Metformin does not address the inflammatory pathways central to HS pathophysiology (TNF-alpha, IL-17, IL-1) and therefore cannot replace targeted immunomodulatory therapies in severe disease. 5

Comparative Effectiveness

Among hormonal/metabolic treatments for HS, response rates are: 6

• Finasteride: 62.8% improvement
• Spironolactone: 50.5% improvement
• Metformin: 46.0% improvement
• Cyproterone acetate: 53.3% improvement

This positions metformin as moderately effective compared to other hormonal therapies, though all lack the robust evidence base of antibiotics and biologics. 6