Insulin Dosing for Severe Hyperglycemia
For a 59kg patient with blood glucose of 700 mg/dL, initiate a continuous IV insulin infusion at 5.9 units/hour (0.1 units/kg/hour) after first administering an IV bolus of 8.85 units (0.15 units/kg), provided serum potassium is ≥3.3 mEq/L. 1
Initial Assessment and Bolus Dosing
Before starting insulin therapy, you must verify that serum potassium is at least 3.3 mEq/L, as insulin therapy will drive potassium intracellularly and can precipitate life-threatening hypokalemia if started when potassium is already low 1. If potassium is below this threshold, hold insulin and aggressively replace potassium first.
The initial IV bolus dose is 0.15 units/kg body weight, which equals 8.85 units for this 59kg patient 1. This bolus achieves rapid therapeutic insulin levels (peak ~460 microU/mL within 5 minutes) and initiates immediate glucose lowering 2.
Continuous Infusion Rate
Following the bolus, start continuous IV infusion at 0.1 units/kg/hour, which equals 5.9 units/hour (approximately 6 units/hour in practice) for this patient 1. This low-dose regimen typically decreases plasma glucose at 50-75 mg/dL per hour 1.
Alternative Without Bolus
If you choose to omit the priming bolus, you must double the infusion rate to 0.14 units/kg/hour (approximately 8.3 units/hour for this patient, or about 8-10 units/hour) to achieve adequate insulin levels 2. However, the standard approach with bolus is preferred as it provides more predictable pharmacokinetics 1.
Monitoring and Titration Algorithm
- Check blood glucose hourly during the first 2-4 hours 1
- If glucose does not fall by at least 50 mg/dL in the first hour, verify adequate hydration status, then double the insulin infusion rate every hour until achieving a steady decline of 50-75 mg/dL per hour 1
- Check serum potassium every 2-4 hours and maintain between 4-5 mEq/L by adding potassium to IV fluids 3, 4
Transition to Dextrose-Containing Fluids
When blood glucose reaches 250 mg/dL, switch IV fluids to 5% dextrose with 0.45-0.75% NaCl while continuing the insulin infusion 3, 4. This prevents hypoglycemia while allowing continued insulin therapy to resolve any underlying ketoacidosis or metabolic derangement 1.
The goal is to maintain glucose between 150-200 mg/dL until complete metabolic resolution (if DKA: pH >7.3, bicarbonate >15 mEq/L) 3.
Critical Pitfalls to Avoid
Never start insulin if potassium is <3.3 mEq/L - this can cause fatal cardiac arrhythmias 1. Aggressively replace potassium first, as insulin therapy will further lower serum potassium levels.
Do not stop IV insulin abruptly when transitioning to subcutaneous insulin. You must continue the IV infusion for 1-2 hours after administering subcutaneous basal insulin to ensure adequate overlap and prevent rebound hyperglycemia 1, 3.
Avoid targeting glucose <140 mg/dL during acute management, as this increases hypoglycemia risk without improving outcomes 1, 5. The target range of 140-180 mg/dL is appropriate for most hospitalized patients 1, 5.
Context-Specific Considerations
With a glucose of 700 mg/dL, this patient likely has either diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS) 1. The insulin dosing remains the same, but you must simultaneously address:
- Aggressive fluid resuscitation with 0.9% NaCl initially (15-20 mL/kg/hour for the first 1-2 hours) 1
- Potassium replacement in every liter of IV fluid once urine output is established and potassium is <5.3 mEq/L 1, 3
- Frequent monitoring of electrolytes, renal function, and acid-base status every 2-4 hours 1
The continuous IV insulin infusion remains the gold standard for severe hyperglycemia because it provides predictable pharmacokinetics with rapid onset and offset, allowing precise titration 1, 6. Subcutaneous insulin is inappropriate in this setting due to unpredictable absorption, especially if the patient has poor perfusion or volume depletion 7.