Situation: A 22-year-old woman with type 1 diabetes mellitus is brought to the emergency department after two days of vomiting, during which she stopped taking her insulin. She weighs 58 kg. Diabetic ketoacidosis (DKA) is diagnosed, and she is admitted to the intensive care unit. Regular insulin is to run at 0.1 units/kg/h. The pharmacy sends 50 units of regular insulin in 100 mL of 0.9% sodium chloride. At what rate should the nurse set the infusion pump? Round off to one decimal place.

The dose is 0.1 units/kg/h × 58 kg = 5.8 units/h. The concentration is 50 units ÷ 100 mL = 0.5 unit/mL. The rate is 5.8 units/h ÷ 0.5 unit/mL = 11.6 mL/h.

Calculating the Insulin Infusion Rate

The prescribed insulin dose is weight-based at 0.1 units/kg/h. For a patient weighing 58 kg, the required hourly dose is calculated as:

0.1 units/kg/h × 58 kg = 5.8 units/h

The pharmacy-prepared solution contains 50 units of regular insulin diluted in 100 mL of 0.9% sodium chloride. This yields a concentration of:

50 units ÷ 100 mL = 0.5 units/mL

To deliver 5.8 units/h using a solution with 0.5 units/mL, the infusion pump rate is:

5.8 units/h ÷ 0.5 units/mL = 11.6 mL/h

Key point! Always confirm the concentration on the pharmacy label before programming the pump. A common error is using the total volume (100 mL) as the hourly rate, which would deliver the entire 50 units in one hour — a massive overdose. The correct rate reflects only the dose needed per hour.

Watch out! In DKA, regular insulin is given as a continuous intravenous infusion because its short half-life allows rapid titration. The infusion is typically continued until the anion gap closes and blood glucose stabilizes, not simply until glucose normalizes. Frequent blood glucose monitoring (usually hourly) guides rate adjustments.

Calculation Step	Formula	Result
Hourly insulin dose	0.1 units/kg/h × 58 kg	5.8 units/h
Solution concentration	50 units ÷ 100 mL	0.5 units/mL
Infusion pump rate	5.8 units/h ÷ 0.5 units/mL	11.6 mL/h

The 2024 ADA/EASD consensus report on hyperglycemic crises emphasizes that intravenous regular insulin should be administered as a continuous infusion, with the initial rate based on weight and adjusted according to serial glucose and ketone measurements ^[1]. The dosing approach in this question — 0.1 units/kg/h — aligns with the guideline-recommended starting range for adult DKA management. Accurate pump programming is a direct nursing responsibility that prevents both under-treatment (persistent ketosis) and over-treatment (hypoglycemia, hypokalemia).