Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease often associated with metabolic disorders such as diabetes mellitus. Recent research suggests a link between systemic inflammation and insulin-glucose dysregulation in HS. This study investigates the relationship between insulin-glucose homeostasis, diabetes mellitus and the haptoglobin concentration in HS patients. We assessed 95 HS patients and 49 controls using validated fasting-based function tests, including the Structural Parameter Inference Approach (SPINA), Homeostasis Model Assessment (HOMA) and Quantitative Insulin Sensitivity Check Index (QUICKI). The HS patients had a significantly higher fasting insulin concentration (97.2 vs. 69.0 pmol/L, = 0.035), increased insulin resistance (HOMA-IR: 3.47 vs. 2.57, = 0.016) and impaired insulin sensitivity (SPINA-GR: 1.34 vs. 1.76 mol/s, = 0.017). In diabetes, the insulin sensitivity was more strongly reduced (SPINA-GR: 0.61 vs. 1.41 mol/s, = 0.0057) and the insulin resistance increased (HOMA-IR: 7.3 vs. 3.2, = 0.017). Higher haptoglobin concentrations were accompanied by worse glycaemic control, demonstrating a significantly elevated fasting glucose (5.77 vs. 5.11 mmol/L, = 0.043) concentration and HbA1c (5.7% vs. 5.4%, = 0.0081) fraction. Our findings suggest that chronic inflammation in HS contributes to metabolic dysregulation, worsening insulin resistance and glycaemic control, particularly in those with elevated haptoglobin or diabetes.