Rescue Dosing of Humulin R (Regular Insulin)
For rescue dosing of hyperglycemia in hospitalized patients, administer regular insulin subcutaneously at 0.1 units/kg as a bolus dose, or give 6 units subcutaneously for pre-prandial glucose ≥16.5 mmol/L (≥300 mg/dL) without ketosis, with repeat glucose monitoring in 3 hours. 1
Subcutaneous Administration
Standard Rescue Dosing Protocol
- Give 0.1 units/kg subcutaneously as a bolus for acute hyperglycemia management 2
- Alternative fixed-dose approach: 6 units of regular insulin subcutaneously when pre-prandial glucose is ≥16.5 mmol/L (≥300 mg/dL) and ketonuria is absent 1
- Administer 30 minutes before meals when used for scheduled correction 3
- Monitor blood glucose 3 hours after administration to assess response 1
Absorption Characteristics
- Subcutaneous injection produces peak insulin levels of 36-45 µU/mL at 50-90 minutes with a 23-35% drop in plasma glucose 4, 5
- Intramuscular injection provides faster absorption than subcutaneous (peak at 50 minutes vs 90 minutes) but is not routinely recommended 5
- Inject into abdominal wall for fastest absorption, followed by thigh, gluteal region, or upper arm 3
Ketosis Considerations
- If ketonuria is 1+ (ketonemia 0.5-1.5 mmol/L): Give 6 units subcutaneously and recheck glucose and ketones in 3 hours 1
- If ketonuria is 2+ (ketonemia ≥1.5 mmol/L): Transfer to ICU for intravenous insulin infusion 1
Intravenous Administration
Critical Care Settings
- Continuous IV insulin infusion is the standard of care for critically ill and mentally obtunded patients with severe hyperglycemia or DKA 6, 7, 8
- Use concentrations of 0.1-1.0 units/mL in 0.9% sodium chloride via polyvinyl chloride infusion bags 3
- Start with 0.05-0.1 units/kg/hour as continuous infusion for moderate to severe DKA 6, 2
Bolus Dosing for DKA
- Give initial "priming" dose of 0.4-0.6 units/kg for mild DKA, with half as IV bolus and half subcutaneously or intramuscularly 2
- Alternative: 0.1 units/kg IV bolus if there is delay in setting up continuous infusion 6
- Follow with 0.1 units/kg/hour subcutaneously or intramuscularly for mild DKA 2
Pharmacokinetics
- IV administration produces maximum insulin concentration of 2099 µU/mL at 2 minutes with 68% glucose drop at 30 minutes 5
- Plasma glucose returns to baseline after 3.5 hours following IV bolus 4
- Much more rapid but shorter-lived response compared to subcutaneous or intramuscular routes 4
Transition from IV to Subcutaneous
Critical Timing
- Administer basal insulin 2-4 hours before stopping IV insulin to prevent rebound hyperglycemia and recurrent ketoacidosis 9, 6, 7, 8
- Calculate subcutaneous dose as 60-80% of total 24-hour IV insulin requirement 10
- Give half as basal insulin once daily in the evening and divide the other half into three equal prandial doses 1
Monitoring Requirements
- Check blood glucose every 2-4 hours during IV insulin infusion 9, 6
- Monitor every 1-2 hours for most patients receiving insulin infusion to prevent hypoglycemia 11
- Continue IV insulin for 1-2 hours after starting subcutaneous regimen to ensure adequate plasma insulin levels 2
Important Caveats
Hypoglycemia Risk
- Nearly 20% of patients experience hypoglycemia with insulin rescue dosing 12
- Administer 50-60 grams of glucose when giving 10-20 units of insulin to prevent hypoglycemia 12
- Use titrated dextrose replacement: (100 - blood glucose) × 0.2 grams of 50% dextrose 11
Route Selection
- IV route is preferred in critical illness (DKA, HHS, severe hyperglycemia >300 mg/dL) 6, 2, 8
- Subcutaneous route is acceptable for mild-moderate hyperglycemia without ketosis or mental status changes 2, 8
- No significant difference in outcomes between IV regular insulin and subcutaneous rapid-acting analogs for mild-moderate DKA when combined with aggressive fluid management 9, 7, 8