Aim To determine the amount of additional insulin required for a high‐protein meal to prevent postprandial hyperglycaemia in individuals with type 1 diabetes using insulin pump therapy. Methods In this randomized cross‐over study, 26 participants aged 8–40 years, HbA1c < 65 mmol/mol (8.1%), received a 50 g protein, 30 g carbohydrate, low‐fat (< 1 g) breakfast drink over five consecutive days at home. A standard insulin dose (100%) was compared with additional doses of 115, 130, 145 and 160% for the protein, in randomized order. Doses were commenced 15‐min pre‐drink and delivered over 3 h using a combination bolus with 65% of the standard dose given up front. Postprandial glycaemia was assessed by 4 h of continuous glucose monitoring. Results The 100% dosing resulted in postprandial hyperglycaemia. From 120 min, ≥ 130% doses resulted in significantly lower postprandial glycaemic excursions compared with 100% (P < 0.05). A 130% dose produced a mean (sd) glycaemic excursion that was 4.69 (2.42) mmol/l lower than control, returning to baseline by 4 h (P < 0.001). From 120 min, there was a significant increase in the risk of hypoglycaemia compared with control for 145% odds ratio (OR) 25.4, 95% confidence interval (CI) 5.5–206; P < 0.001) and 160% (OR 103, 95% CI 19.2–993; P < 0.001). Some 81% (n = 21) of participants experienced hypoglycaemia following a 160% dose, whereas 58% (n = 15) experienced hypoglycaemia following a 145% dose. There were no hypoglycaemic events reported with 130%. Conclusions The addition of 30% more insulin to a standard dose for a high‐protein meal, delivered using a combination bolus, improves postprandial glycaemia without increasing the risk of hypoglycaemia. What’s new? Consumption of protein can lead to delayed and sustained postprandial hyperglycaemia and increased insulin demand; however, it is not known how much additional insulin is required for high‐protein meals containing carbohydrate. This research investigated the effects of additional insulin for a 50 g protein, 30 g carbohydrate, non‐fat meal Findings indicate that a 30% increased dose, delivered using a combination bolus, improved postprandial glycaemia without increasing the risk of hypoglycaemia. When increased doses of ≥ 45% were given there was statistically significantly increased hypoglycaemia. These findings support recommendations to consider additional insulin doses for meals containing large amounts of protein.