To evaluate the impact of switching from U-100 to U-500 insulin in patients with type 2 diabetes mellitus (T2DM) uncontrolled with continuous subcutaneous insulin infusion (CSII) by pump.

We retrospectively collected data from patients with T2DM, treated by U-100 CSII, who were switched to U-500 regular insulin where haemoglobin A1c (Hb_A1c) was >8% and/or insulin total daily dose (TDD) was >100 UI/d. Data collection from patient medical records included Hb_A1c, lipid levels, liver biomarkers, weight, TDD, declared hypoglycaemic episodes and measured by continuous glucose monitoring (CGM).

Sixty-five patients were included, aged 63.9 ± 8.6 years, insulin pump since 3.7 ± 3 years, TDD 186 ± 52 U/day, body mass index 39.4 ± 5.3 kg/m², Hb_A1c 9.03 ± 1.6%. After switching to U-500 insulin, Hb_A1c dropped by -0.96% (P < 0.0001) at one year with the effect maintained at three years (- 0.95%, P < 0.01). A subgroup analysis (n=42/65) using a severity score which covered the three previous years on U-100 and the next three years on U-500 insulin confirmed the latter's efficacy. Body weight increased by + 4.8 kg and TDD by 16% at three years. Declared non-severe hypoglycaemia increased significantly three- to four-fold during follow up, but % time-below-range at six months did not differ between the two treatments. Baseline Hb_A1c correlated with improved glucose control with U-500.

U-100 to U-500 insulin switch improves glucose control in CSII T2DM patients, especially with high baseline Hb_A1c. Use of concentrated insulin in pumps may represent an advance in the strategy for treating T2DM insulin resistant states with uncontrolled hyperglycaemia after a switch from multiple daily injections to pump therapy.