Priming Insulin Infusions: 20 mL Standard Protocol
Prime all new insulin infusion tubing with exactly 20 mL of the insulin solution as waste before connecting to the patient. 1, 2
Standard Preparation Method
Prepare the infusion at 1 unit/mL concentration using regular human insulin in 0.9% normal saline for all continuous IV insulin infusions. 1, 2
Flush 20 mL through the tubing as waste before initiating therapy to saturate insulin binding sites in the IV tubing and ensure accurate insulin delivery. 1, 2
This 20 mL priming volume is sufficient to minimize insulin adsorption losses to IV lines, with insulin concentrations becoming indistinguishable from maximal values after this volume. 3
Why 20 mL Is the Evidence-Based Standard
The 20 mL recommendation balances efficacy with waste reduction:
Without priming, insulin delivery is only 84% of intended dose due to adsorption to plastic tubing. 3
After 10 mL prime, 6.6% insulin loss remains, which is marginally significant and clinically relevant. 3
After 20 mL prime, insulin loss drops to 3.4% and becomes statistically indistinguishable from maximal saturation. 3
Priming volumes exceeding 20 mL provide no additional benefit and unnecessarily waste insulin, increase costs, and generate extra work. 3
Critical Pitfalls to Avoid
Never use rapid-acting or long-acting insulin analogs for IV infusions—only regular human insulin is appropriate for intravenous administration. 1, 2, 4
Do not skip the priming step, especially at low flow rates (<1 mL/h), where up to 50% of intended insulin may not be delivered over 24 hours due to adsorption. 5
At very low flow rates (0.05-0.2 mL/h), consider priming with higher concentration insulin (5 units/mL for 20 minutes) before starting the standard 1 unit/mL infusion to accelerate steady-state delivery, particularly in neonatal or pediatric settings. 6
Inspect the insulin solution before use—it must be clear and colorless; any cloudiness, clumping, or discoloration indicates loss of potency and the vial must be replaced. 2, 4
Material Considerations
Both polyvinyl chloride (PVC) and polyethylene-lined tubing require the same 20 mL priming volume, as both materials exhibit similar insulin adsorption characteristics at standard flow rates. 3, 6
Insulin adsorption capacity increases dramatically as flow rate decreases—when flow rate is halved from 1 to 0.5 mL/h, twice as much insulin adheres to the tubing. 5