OBJECTIVES: Data on wastage behaviours of patients with diabetes taking mealtime insulin (MTI) with a prefilled disposable pen or reusable pen with disposable cartridge are lacking. A patient survey was undertaken to estimate the average number of MTI units discarded per pen/cartridge by patients with diabetes taking >20 units/day, based on injection habits when insufficient insulin remains in a pen/cartridge to administer a full dose in a single injection. METHODS: Cross-sectional, online, self-reported survey of MTI usage and wastage behaviours in adults with type 1 or 2 diabetes [T1D, T2D] using >20 units/day of MTI administered via 100 units/mL pen/cartridge for ≥1 month, conducted between February and March 2015 in four EU countries [France, Germany, Italy, United Kingdom]. RESULTS: [T1D: 26.9 (4.9); T2D: 31.3 (7.7)]. Average time since diabetes diagnosis was 16.1 (11.7) years [T1D: 23.4 (14.2); T2D: 13.0 (8.8)]. Total average MTI units taken per day (self-reported number of units taken at breakfast, lunch and dinner combined) was 54.8 (34.1) units [T1D: 41.1 (21.9); T2D: 60.6 (36.7)].  255 patients [63.8%] reported wasting no insulin, whereas 145 patients [36.3%] reported wasting some insulin. Overall, patients reported discarding 2.0 [95% CI 1.4–2.5] pens/cartridges per month on average that still had insulin remaining. Patients who reported wasting some insulin discarded on average 8.6 [95% CI 7.2–10.0] units of MTI per pen/cartridge. CONCLUSIONS: One third of patients taking >20 units/day MTI reported discarding at least one 100 units/mL pen/cartridge with insulin remaining. These results suggest there may be an opportunity to reduce insulin wastage with new higher strength MTI formulations that provide more total units per pen and fewer pen/cartridge transitions.