What is the proper protocol for administering insulin infusion to a patient?

How to Give Insulin Infusion

Preparation Protocol

Prepare insulin infusions at a standardized concentration of 1 unit/mL using regular human insulin in 0.9% normal saline, and prime the tubing with 20 mL of waste volume before connecting to the patient. 1, 2

• Regular human insulin is the only appropriate formulation for IV administration; other insulin types (rapid-acting analogs, long-acting) cause unpredictable pharmacokinetics and must never be used intravenously 1
• The 1 unit/mL concentration minimizes dosing errors and allows consistent titration across all critically ill patients 1, 2
• Priming with 20 mL waste volume is essential because insulin adsorbs to IV tubing material initially, and this step ensures accurate dosing from the start 1, 2

Storage and Handling

• Store unopened insulin vials refrigerated at 36-46°F (2-8°C) to prevent loss of potency 1
• Inspect vials immediately before use—insulin must appear completely clear and colorless; any cloudiness or discoloration indicates loss of potency and the vial must be discarded 1
• Once prepared, infusions remain stable at room temperature for 24 hours 1
• Run insulin through dedicated IV tubing without mixing other medications in the same line unless specifically approved by pharmacy 1, 2

Clinical Indications for IV Insulin

Use IV insulin infusion for hemodynamically unstable patients requiring vasopressors, all patients with type 1 diabetes in critical care, and any situation requiring rapid titration for tight glycemic control. 2

• Do not use IV insulin for stable, non-critically ill patients who can be managed with subcutaneous regimens 2
• IV insulin is mandatory for diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) 2

Dosing Initiation

For DKA, start at 0.1 units/kg/hour as continuous infusion only after confirming serum potassium >3.3 mmol/L. 1

• For general critical care hyperglycemia, most protocols use initial rates of 0.5-1 unit/hour with titration based on hourly glucose monitoring 1, 2
• Never give IV insulin as bolus injections; it must be administered as continuous infusion 2

Glucose Monitoring During Infusion

• Measure blood glucose hourly using point-of-care testing during active titration 2
• Target glucose 140-180 mg/dL in critically ill patients to balance glycemic control against hypoglycemia risk 2
• Maintain stable glucose levels for at least 24 hours before considering transition to subcutaneous insulin 2

Nutritional Considerations

• Evaluate the amount and timing of carbohydrate intake (enteral, parenteral, or dextrose-containing IV fluids) when calculating insulin requirements 2
• Protocols must include instructions for unplanned discontinuation of nutrition—if dextrose infusion stops unexpectedly, reduce or temporarily stop insulin infusion to prevent hypoglycemia 2
• For patients receiving parenteral nutrition with >200-300 g dextrose daily, insulin requirements will be substantially higher 2

Transition to Subcutaneous Insulin

Administer subcutaneous basal insulin 2 hours before discontinuing the IV infusion to prevent rebound hyperglycemia. 2

• Calculate the basal insulin dose based on the IV insulin infusion rate during the last 6 hours when stable glycemic goals were achieved 2
• The most widely used transition model: give half the total 24-hour IV insulin dose as long-acting subcutaneous insulin, with the other half as rapid-acting analog divided before meals 2
• Alternative approach: give 80% of the 24-hour IV insulin dose as basal insulin and add rapid-acting insulin at the first meal 2
• Only transition when glucose levels are stable <180 mg/dL for 24 hours, oral feeding has resumed, peripheral edema has resolved, and the patient is off vasopressors 2
• If IV insulin rate is >5 units/hour, this indicates severe insulin resistance and the patient should remain on IV infusion 2

Common Pitfalls to Avoid

• Never stop IV insulin before giving subcutaneous basal insulin—this causes dangerous rebound hyperglycemia within hours 2
• Do not use sliding scale insulin alone as the transition regimen; it provides inadequate glycemic control and increases complications 2
• Avoid mixing insulin with other medications in the same IV line, as compatibility issues can alter insulin delivery 1, 2
• Do not use concentrated insulin formulations (U-200, U-300, U-500) for IV infusions—only regular U-100 insulin is appropriate 2