Insulin Infusion Priming Protocol
Prime insulin infusion tubing with the standard 1 unit/mL insulin solution (not diluted or "raw" concentrated insulin), using a 20-mL waste volume before connecting to the patient. 1, 2
Standard Preparation and Priming Method
The American College of Critical Care Medicine establishes the definitive approach: prepare continuous insulin infusions at a standardized concentration of 1 unit/mL using regular human insulin in 0.9% normal saline, then prime new tubing with a 20-mL waste volume. 1, 2 This means you prime with the same solution you will infuse—not with undiluted insulin from the vial or a different concentration.
Why 20 mL of Prime is Optimal
Research directly addressing this question demonstrates that:
- Without priming, insulin adsorption to IV tubing causes 15.8% loss of insulin concentration 3
- After 10 mL of prime, losses decrease to 6.6% (marginally significant) 3
- After 20 mL of prime, insulin concentrations become indistinguishable from maximal values (only 3.4% loss) 3
- Priming volumes exceeding 20 mL are wasteful and generate unnecessary work 3
The adsorption problem is substantial: insulin adsorbs to PVC infusion sets at rates up to 57%, while polypropylene bags show minimal adsorption (≤5%). 4 The 20-mL flush effectively saturates the binding sites in the tubing before patient administration begins.
Step-by-Step Priming Protocol
Prepare the infusion: Mix regular human insulin to 1 unit/mL concentration in 0.9% sodium chloride 1, 2, 5
Inspect the insulin: Verify it appears clear and colorless; never use if viscous, cloudy, or discolored 2, 5
Prime the tubing: Flush 20 mL of the prepared 1 unit/mL solution through new IV tubing as waste 1, 2, 3
No dwell time needed: After the 20-mL flush, you can start the infusion immediately without waiting 6
Connect to patient: Begin infusion at prescribed rate
Critical Pitfalls to Avoid
Never prime with concentrated insulin directly from the vial. The question of "raw insulin" versus diluted refers to whether you use undiluted insulin from the vial (typically U-100, meaning 100 units/mL) or the prepared infusion solution. The answer is unequivocal: always prime with the prepared 1 unit/mL solution that matches what the patient will receive. 1, 2
Do not use alternative priming methods with higher insulin concentrations. While one neonatal study suggested priming with 5 units/mL insulin solution improved delivery in extremely low birth weight infants at very slow flow rates (0.05-0.2 mL/h), 7 this approach is not endorsed by critical care guidelines and applies only to specialized neonatal scenarios with microbore tubing—not standard adult ICU practice.
Avoid inadequate priming volumes. Some older protocols recommended up to 50 mL of prime, but this wastes expensive medication and solution. 3 The evidence-based sweet spot is exactly 20 mL. 1, 2, 3
Material Considerations
If available, use polypropylene infusion sets rather than polyvinyl chloride (PVC), as PVC shows dramatically higher insulin adsorption (57% vs ≤5%). 4 However, the 20-mL priming protocol adequately addresses adsorption regardless of tubing material. 3
The prepared insulin solution remains stable for 48 hours refrigerated, then an additional 48 hours at room temperature. 5