Can Metformin Be Used to Treat Hidradenitis Suppurativa?
Metformin should be considered as an adjunctive treatment option for patients with hidradenitis suppurativa, particularly in those with concomitant diabetes mellitus, polycystic ovary syndrome (PCOS), or features of metabolic syndrome. 1
Guideline-Based Recommendations
The British Association of Dermatologists (2019) provides the clearest guidance: consider metformin in people with HS with concomitant diabetes mellitus, and females with HS and polycystic ovary syndrome or pregnancy. 1 This recommendation carries a Good Practice Point (GPP) rating, indicating consensus-based expert opinion rather than high-quality trial evidence.
The North American guidelines (2019) similarly position metformin as a hormonal therapy option, noting it should be considered as monotherapy in females with mild-to-moderate HS or as adjunctive therapy for more severe disease, with particular benefit expected in patients reporting HS flares around menses or with features of PCOS. 1
Evidence Supporting Metformin Use
Clinical Efficacy Data
The strongest prospective evidence comes from a 24-week uncontrolled study of 25 patients (22 females with PCOS features) treated with metformin 500 mg 2-3 times daily, which demonstrated significant improvement in Sartorius score in 72% (18/25 patients) and DLQI score in 64% (16/25 patients). 1
A retrospective chart review of 53 HS patients treated with metformin (mean dose 1.5 g/day for 11.3 months) showed subjective clinical response in 68%, with 19% achieving quiescent disease on metformin monotherapy alone. 2 The drug was well tolerated with only 11% experiencing gastrointestinal side effects. 2
Mechanism of Action
Metformin's benefit in HS likely stems from multiple mechanisms: improving hyperinsulinemia (present in 75% of HS patients), reducing insulin resistance, providing antiandrogenic effects, and potentially offering anti-inflammatory properties. 2, 3 These mechanisms address the metabolic dysfunction frequently associated with HS.
Treatment Algorithm for Metformin in HS
When to Consider Metformin
Primary indications:
- Female patients with HS and documented PCOS or features suggesting hyperandrogenism 1
- Patients with HS and concomitant type 2 diabetes mellitus 1
- Patients with HS and metabolic syndrome features (obesity, insulin resistance) 2, 3
- Patients reporting HS flares correlating with menstrual cycles 1
Role in treatment hierarchy:
- Use as adjunctive therapy alongside first-line antibiotics (topical clindamycin or oral tetracyclines) for mild-to-moderate disease 1
- Consider as monotherapy only in mild disease with clear metabolic/hormonal features 1
- Not appropriate as monotherapy for severe disease (Hurley Stage III) 1
Dosing and Monitoring
Standard dosing: Start metformin 500 mg twice daily, titrating up to 500 mg three times daily (1500 mg/day total) as tolerated. 1, 2 This matches the dose used in the prospective trial showing benefit.
Duration: Treat for at least 24 weeks before assessing response, as this was the duration in the primary prospective study. 1 The retrospective study showed mean treatment duration of 11.3 months with 6-month drug survival of 61%. 2
Response assessment: Measure treatment response at 12-24 weeks using pain scores (Visual Analog Scale), inflammatory lesion count, and quality of life measures (DLQI). 1
Critical Limitations and Caveats
Evidence Quality Issues
The evidence supporting metformin in HS is notably weak compared to other HS treatments. The British guidelines rate it as GPP (Good Practice Point) rather than evidence-graded, and the 2019 guidelines explicitly state "insufficient evidence to recommend" metformin as a standalone recommendation for general HS populations. 1 The North American guidelines position it specifically within hormonal therapies based on "limited evidence." 1
When NOT to Use Metformin
Contraindications specific to HS context:
- Patients with cirrhosis (increased risk of metabolic acidosis and ascites) 1
- Severe HS (Hurley Stage III) requiring aggressive systemic therapy—metformin is insufficient as monotherapy 1
- Male patients without diabetes, where evidence is particularly limited 1
Predictive Factors
Importantly, the presence of insulin resistance did NOT predict clinical response to metformin in the retrospective study, meaning you cannot use insulin resistance testing to select responders. 2 However, clinical features of PCOS or metabolic syndrome remain reasonable selection criteria based on the study populations showing benefit. 1, 2
Positioning Relative to Other Treatments
Metformin should not replace evidence-based first-line therapies. For moderate disease, clindamycin 300 mg twice daily plus rifampicin 300-600 mg daily for 10-12 weeks remains the superior first-line choice with response rates of 71-93%. 1 For severe disease unresponsive to antibiotics, adalimumab is the evidence-based first-line biologic with strong recommendation ratings. 1
Metformin functions best as an adjunctive agent targeting the metabolic/hormonal component of HS pathophysiology, not as a replacement for anti-inflammatory or antimicrobial therapies. 1, 4
Practical Implementation
Combination approach: When prescribing metformin for HS, combine it with appropriate first-line therapy based on disease severity—topical clindamycin for mild disease or oral antibiotics for moderate disease. 1 Address essential adjunctive measures including smoking cessation referral, weight management, pain control with NSAIDs, and screening for depression/anxiety. 1
Safety profile: Metformin demonstrates a favorable safety profile in HS populations, with gastrointestinal side effects being the primary concern (11% in the largest retrospective series). 2 No serious adverse effects have been reported in dermatologic applications. 4
Cost consideration: Metformin is inexpensive and widely available, making it an attractive adjunctive option for appropriate patients. 2