How do you convert an insulin infusion to subcutaneous insulin?

Converting Insulin Infusion to Subcutaneous Insulin

Administer subcutaneous basal insulin 2 hours before discontinuing the IV insulin infusion, using 50% of the total 24-hour IV insulin dose as long-acting basal insulin and dividing the remaining 50% equally as rapid-acting insulin before each meal. 1

Calculate the Total Daily Dose

• Determine the average hourly IV insulin infusion rate during the prior 6-8 hours when glucose levels have been stable (ideally 100-180 mg/dL), then multiply by 24 to calculate the total daily insulin requirement 1
• For example, if a patient received an average of 1.5 units/hour during stable glycemic control, the estimated total daily dose would be 36 units (1.5 × 24 = 36 units) 1
• Alternative calculation methods include using 80% of the 24-hour IV insulin total or a weight-based approach of 0.3-0.5 units/kg for insulin-naive patients, though the 6-8 hour stable rate method is preferred 1, 2

Divide Into Basal and Prandial Components

• Give 50% of the calculated total daily dose as once-daily long-acting basal insulin (glargine, detemir, or degludec) administered subcutaneously 1, 3
• Divide the remaining 50% equally into three doses of rapid-acting insulin (lispro, aspart, or glulisine) to be given before each meal 1, 3
• Using the example above with 36 units total: give 18 units of basal insulin once daily, plus 6 units of rapid-acting insulin before each of the three meals 1, 3

Critical Timing to Prevent Rebound Hyperglycemia

• Administer the first dose of subcutaneous basal insulin exactly 2 hours before stopping the IV insulin infusion to allow adequate absorption and prevent dangerous rebound hyperglycemia 1, 3
• This 2-hour overlap is non-negotiable—stopping IV insulin without prior subcutaneous basal coverage is associated with increased morbidity and higher costs of care 1
• Some protocols suggest administering low-dose basal insulin (0.15-0.3 units/kg) concurrently with the IV infusion during the final 12-24 hours to further reduce rebound hyperglycemia risk, though this is optional 1

Add Correctional Insulin

• Prescribe supplemental rapid-acting insulin using a correction scale to address hyperglycemia between scheduled doses 1
• A typical correction factor is 1 unit of rapid-acting insulin per 50 mg/dL above target glucose (e.g., if target is 120 mg/dL and current glucose is 220 mg/dL, give 2 units correction dose) 4
• Administer correction doses before meals (added to the scheduled prandial dose) or every 4-6 hours if the patient is not eating 1

Prerequisites Before Transition

• Ensure glucose levels have been stable for at least 4-6 hours consecutively on the IV insulin infusion before initiating transition 1, 4
• Confirm hemodynamic stability (not requiring vasopressors) and that the patient has a stable nutrition plan or is able to eat 1
• Verify resolution of any acute metabolic crisis such as DKA (pH >7.3, bicarbonate ≥18 mEq/L, anion gap ≤12 mEq/L) or HHS (serum osmolality <315 mOsm/kg) before transitioning 3, 4

Special Populations Requiring Dose Adjustment

• Reduce the starting dose to 0.15-0.2 units/kg total daily dose (rather than 0.3-0.5 units/kg) in elderly patients (>65 years), those with renal insufficiency, or patients with poor oral intake to minimize hypoglycemia risk 1
• For patients with known diabetes previously on insulin at home, reduce their home total daily dose by 20% rather than calculating from IV insulin rates, as acute illness typically increases insulin requirements temporarily 1
• In patients with renal failure, expect decreased insulin clearance and monitor more frequently for hypoglycemia, as this is a major risk factor for severe hypoglycemia in hospitalized patients 1

Intensive Monitoring Requirements

• Check capillary blood glucose before each meal and at bedtime (minimum 4 times daily) during the first 24-48 hours after transition 1, 5
• Monitor serum potassium closely as subcutaneous insulin continues to drive potassium intracellularly, potentially causing life-threatening hypokalemia and cardiac arrhythmias 4, 6
• Adjust insulin doses daily based on glucose patterns—if fasting glucose is elevated, increase basal insulin by 10-20%; if postprandial glucose is elevated, increase the corresponding prandial dose 1

Common Pitfalls to Avoid

• Never stop the IV insulin infusion before administering subcutaneous basal insulin—this single error causes rebound hyperglycemia, recurrent DKA/HHS, and increased hospital complications 1, 3, 4
• Never use sliding scale (correction-only) insulin alone without scheduled basal and prandial insulin in patients with known diabetes, as this approach is associated with worse outcomes and higher complication rates 1, 4
• Never mix different insulin formulations in the same syringe except NPH with rapid-acting insulin (draw rapid-acting first), and never mix insulins in pump reservoirs 6
• Do not use the same total daily dose calculation if the IV infusion was brief (<24 hours)—instead use weight-based dosing of 0.3-0.5 units/kg for insulin-naive patients 1

Alternative Dosing Strategies When Evidence Conflicts

• While the 50/50 split (50% basal, 50% prandial) is most widely recommended 1, 3, one older study suggested using 80% of the 24-hour IV insulin total as basal insulin alone achieved better glycemic control 2
• However, the 80% approach was studied only in the immediate 24-hour post-transition period and did not account for nutritional insulin needs, making the 50/50 basal-bolus approach more physiologic and safer for ongoing management 1
• For patients not eating or on continuous enteral nutrition, consider giving 80% of the calculated dose as basal insulin only with correction doses every 4-6 hours, then transition to basal-bolus when oral intake resumes 1