What is the recommended weight‑based intravenous insulin protocol for an adult (≥18 years) presenting with diabetic ketoacidosis or severe hyperglycemia?

Weight-Based Intravenous Insulin Protocol for Diabetic Ketoacidosis

For adults with moderate-to-severe DKA, initiate continuous IV regular insulin at 0.1 units/kg/hour after an optional IV bolus of 0.1 units/kg, targeting a glucose decline of 50-75 mg/dL per hour. 1

Initial Assessment and Insulin Initiation

Critical Pre-Insulin Check

• Do not start insulin if serum potassium is <3.3 mEq/L—this is an absolute contraindication that can cause life-threatening cardiac arrhythmias and death 1
• If K+ <3.3 mEq/L, aggressively replete potassium with 20-40 mEq/L in IV fluids until K+ ≥3.3 mEq/L, then start insulin 1

Standard IV Insulin Protocol

• Bolus dose: 0.1 units/kg IV regular insulin (optional—recent evidence shows no significant benefit but remains in guidelines) 1, 2
• Continuous infusion: 0.1 units/kg/hour IV regular insulin 1
• Target glucose decline: 50-75 mg/dL per hour 1

Adjusting the Infusion Rate

• If glucose does not fall by 50 mg/dL in the first hour, verify adequate hydration status 1
• Double the insulin infusion rate every hour until achieving steady decline of 50-75 mg/dL/hour 1

Concurrent Fluid and Electrolyte Management

Initial Fluid Resuscitation

• Begin with isotonic saline (0.9% NaCl) at 15-20 mL/kg/hour for the first hour 3, 1
• Total fluid replacement should approximate 1.5 times the 24-hour maintenance requirements 3

Potassium Replacement

• Once K+ ≥3.3 mEq/L and renal function is confirmed, add 20-30 mEq/L potassium to each liter of IV fluid 3, 1
• Use a combination of 2/3 KCl or potassium-acetate and 1/3 KPO4 1
• Target serum potassium 4-5 mEq/L throughout treatment 1

Glucose Management During Treatment

Adding Dextrose

• When serum glucose falls to 250 mg/dL, add dextrose 5% to IV fluids while continuing insulin infusion 1, 4
• Target glucose 150-200 mg/dL until complete DKA resolution 1, 4
• Never stop insulin when glucose normalizes—ketonemia takes longer to clear than hyperglycemia, and stopping insulin is a common cause of persistent or worsening ketoacidosis 4

Monitoring Requirements

Laboratory Monitoring

• Check blood glucose every 2-4 hours 1
• Measure serum electrolytes, glucose, BUN, creatinine, osmolality, and venous pH every 2-4 hours until stable 3, 1
• Venous pH is sufficient (typically 0.03 units lower than arterial pH) and avoids repeat arterial punctures 4
• Direct measurement of β-hydroxybutyrate in blood is the preferred method for ketone monitoring 1

DKA Resolution Criteria

All of the following must be met simultaneously: 1, 4

• Glucose <200 mg/dL
• Serum bicarbonate ≥18 mEq/L
• Venous pH >7.3
• Anion gap ≤12 mEq/L

Transition to Subcutaneous Insulin

Critical Timing to Prevent Rebound DKA

• Administer basal insulin (glargine or detemir) subcutaneously 2-4 hours BEFORE stopping the IV insulin infusion—this is the most common error leading to DKA recurrence 3, 1
• Continue IV insulin for 1-2 hours after administering subcutaneous insulin to ensure adequate plasma insulin levels 1, 4

Calculating Subcutaneous Doses

• Total daily dose = Average hourly IV insulin rate over last 12 hours × 24 5
• Basal insulin = 50% of total daily dose given as glargine or detemir once daily 5
• Prandial insulin = 50% of total daily dose divided equally before three meals as rapid-acting analog 5

Alternative Simplified Calculation

• Basal insulin = 1/2 of the 24-hour IV insulin dose given as long-acting insulin 3
• Prandial insulin = 1/2 of the 24-hour IV insulin dose divided by 3 for each meal 3

Alternative Approach for Mild-Moderate Uncomplicated DKA

For hemodynamically stable, alert patients with mild-moderate DKA: 3, 1

• Subcutaneous rapid-acting insulin analogs combined with aggressive fluid management can be as effective and more cost-effective than IV insulin
• Requires adequate fluid replacement, frequent bedside glucose testing, and appropriate follow-up

Common Pitfalls to Avoid

• Never discontinue IV insulin without prior basal insulin administration—this causes rebound hyperglycemia and recurrent DKA 1
• Never stop insulin when glucose normalizes—continue until all resolution criteria are met 4
• Never use correction-only (sliding scale) insulin alone—this approach leads to worse outcomes 5
• Never start insulin if K+ <3.3 mEq/L—replete potassium first 1
• Never fail to add dextrose when glucose falls below 250 mg/dL—continue insulin to clear ketones 1, 4

Special Consideration: Early Basal Insulin

Recent high-quality evidence suggests that early administration of subcutaneous insulin glargine 0.3 units/kg within the first 3 hours of DKA diagnosis, in addition to standard IV insulin infusion, leads to faster DKA resolution (9.89 vs 12.73 hours) and shorter hospital stay without increasing hypoglycemia or hypokalemia 6. However, this approach is not yet incorporated into standard guidelines and should be considered investigational.