What is the recommended dose for insulin infusion in an adult patient with insulin-dependent diabetes?

Insulin Infusion Dosing for Adult Patients with Insulin-Dependent Diabetes

Critical Care Setting: Continuous IV Insulin Infusion

For critically ill adults with persistent hyperglycemia ≥180 mg/dL, initiate continuous regular insulin infusion at 0.1 units/kg/hour, targeting blood glucose 140-180 mg/dL. 1

Initiation Protocol

• Start IV insulin when blood glucose exceeds 180 mg/dL on two consecutive measurements 1
• Verify serum potassium ≥3.3 mEq/L before starting insulin—correct hypokalemia first to prevent life-threatening cardiac arrhythmias 1
• For severe hyperglycemia >300 mg/dL or DKA, consider IV bolus of 0.15 units/kg before starting the continuous infusion 1
• Use only regular insulin via continuous IV infusion—never use subcutaneous insulin in critically ill patients, especially during hypotension or shock 1

Target Glucose Range

• Maintain blood glucose 140-180 mg/dL for most critically ill adults 2, 1
• More stringent targets of 110-140 mg/dL may be appropriate only for select cardiac surgery patients if achievable without hypoglycemia 2, 1
• Avoid intensive targets <140 mg/dL in unselected critically ill patients—the NICE-SUGAR trial demonstrated this increases mortality 4-fold and severe hypoglycemia 10- to 15-fold without improving outcomes 1

Monitoring Requirements

• Measure blood glucose every 1-2 hours during insulin infusion until stable, then every 2 hours 1
• Monitor serum potassium closely—insulin drives potassium intracellularly; maintain K+ >3.3 mEq/L 1
• Use validated computerized decision support tools or explicit paper protocols to guide insulin titration 1

Non-Critical Care Setting: Subcutaneous Insulin Regimens

For non-critically ill hospitalized patients with persistent hyperglycemia >180 mg/dL, use scheduled subcutaneous basal-bolus insulin rather than IV infusion. 2

Initial Dosing Strategy

• For insulin-naive or low-dose insulin patients: Start with total daily dose of 0.3-0.5 units/kg/day 3
• Give 50% as basal insulin (glargine or detemir) once daily 3
• Give 50% as bolus insulin (rapid-acting analog) divided equally before three meals 3
• For patients on high-dose home insulin ≥0.6 units/kg/day: Reduce total daily dose by 20% upon hospitalization to prevent hypoglycemia 3

High-Risk Populations Require Lower Doses

• For elderly patients >65 years, those with renal failure, or poor oral intake: Use 0.1-0.25 units/kg/day 3
• For patients with CKD Stage 5 and type 2 diabetes: Reduce total daily insulin dose by 50% 3
• For patients with CKD Stage 5 and type 1 diabetes: Reduce total daily insulin dose by 35-40% 3

Correction Insulin Protocol

• Administer regular insulin subcutaneously every 4-6 hours as needed for blood glucose correction 1
• For non-DKA hyperglycemia: Give regular insulin every 6 hours or rapid-acting insulin every 4 hours 1
• Use simplified sliding scale: 2 units for glucose >250 mg/dL, 4 units for glucose >350 mg/dL—but only as adjunct to scheduled basal-bolus therapy, never as monotherapy 3

Transitioning from IV to Subcutaneous Insulin

Administer subcutaneous insulin 1-2 hours before discontinuing IV insulin infusion to prevent rebound hyperglycemia. 2, 1

Transition Dosing

• Calculate total subcutaneous dose as 60-80% of the 24-hour IV insulin infusion rate 2
• Alternative method: Total subcutaneous dose = 1/2 of IV insulin infused over 24 hours 3
• Give 50% as basal insulin once in the evening 3
• Divide remaining 50% by 3 for rapid-acting analog before each meal 3

Critical Pitfalls to Avoid

• Never use sliding scale insulin as monotherapy—it results in dangerous glucose fluctuations and is explicitly condemned by all major diabetes guidelines 2, 1
• Never discontinue IV insulin without prior subcutaneous dosing, especially in patients with type 1 diabetes or DKA—this precipitates rapid metabolic decompensation 1
• Never use subcutaneous insulin in critically ill patients during hypotension or shock—absorption is unpredictable 1
• Never target glucose <140 mg/dL in unselected critically ill patients—this increases mortality without benefit 1
• Never give rapid-acting insulin at bedtime—this significantly increases nocturnal hypoglycemia risk 2, 3

Special Clinical Situations

Enteral/Parenteral Nutrition

• For continuous enteral or parenteral feedings: Calculate nutritional insulin as 1 unit per 10-15 grams of carbohydrate 2
• Give NPH insulin every 8-12 hours to cover nutritional component 2
• Administer correctional insulin subcutaneously every 6 hours with regular human insulin 2
• If enteral nutrition is interrupted, start dextrose infusion immediately to prevent hypoglycemia 2

Glucocorticoid Therapy

• For patients on steroids: Increase prandial and correction insulin by 40-60% or more in addition to basal insulin 2, 3
• For once- or twice-daily steroids: Administer NPH insulin concomitantly with intermediate-acting steroids 2
• For long-acting glucocorticoids like dexamethasone: Long-acting basal insulin may be required to manage fasting blood glucose 2