Do we need to flush the intravenous (IV) set with insulin before starting an insulin infusion?

Priming IV Tubing for Insulin Infusions

Yes, you must prime the IV tubing with insulin solution before starting the infusion, using a 20-mL flush volume to minimize insulin adsorption to the plastic tubing. 1, 2

Why Priming is Necessary

Insulin adsorbs to the plastic materials used in IV tubing, which significantly reduces the concentration of insulin actually delivered to the patient. Without priming, insulin levels can be 15.8% lower than intended concentrations. 2

Optimal Priming Protocol

Use a 20-mL waste/flush volume when initiating insulin infusions:

• After 20 mL of priming, insulin concentrations become indistinguishable from maximal values (only 3.4% loss). 2
• A 10-mL prime reduces losses to 6.6%, but this remains marginally significant. 2
• Priming volumes exceeding 20 mL provide no additional benefit and waste medication unnecessarily. 2

The Critical Care Medicine guidelines specifically recommend: "continuous insulin infusion (1 unit/mL) therapy be initiated after priming new tubing with a 20-mL waste volume." 1

No Dwell Time Required

You do NOT need to let the insulin dwell in the tubing before starting the infusion:

• Research demonstrates that dwell times of 0,15,30, or 60 minutes produce no significant differences in insulin concentrations delivered from the tubing. 3
• Following the 20-mL flush, insulin infusions can be started immediately without any waiting period. 3
• Eliminating dwell time improves clinical efficiency by minimizing preparation time and allows faster treatment initiation. 3

Practical Implementation

Step-by-step approach:

1. Prepare insulin infusion at standard concentration (typically 1 unit/mL). 1
2. Prime the IV tubing with 20 mL of the insulin solution and discard this volume. 1, 2
3. Start the infusion immediately—no dwell time needed. 3
4. Begin hourly glucose monitoring and titrate according to your institution's protocol. 1

Common Pitfall to Avoid

Do not use excessive priming volumes: Some older protocols recommend up to 50 mL of prime, which wastes medication (especially problematic with 100-mL bags), increases costs, and generates unnecessary work for nurses and pharmacists without improving insulin delivery. 2