What is the recommended insulin regimen when switching a patient with diabetic ketoacidosis (DKA) from intravenous (IV) insulin to subcutaneous insulin?

Transitioning from IV to Subcutaneous Insulin in DKA

Administer the first dose of subcutaneous basal insulin 2-4 hours BEFORE discontinuing the IV insulin infusion to prevent rebound hyperglycemia and recurrent ketoacidosis. 1, 2

Prerequisites for Transition

Before transitioning to subcutaneous insulin, ensure ALL of the following criteria are met:

• DKA resolution confirmed: glucose <200 mg/dL, serum bicarbonate ≥18 mEq/L, venous pH >7.3, and anion gap ≤12 mEq/L 1, 2
• Stable glucose measurements for at least 4-6 hours consecutively 3
• Hemodynamic stability (not requiring vasopressors) 3
• Patient able to eat or has a stable nutrition plan 3, 2
• Normal potassium levels maintained (4-5 mEq/L) 1

Calculating Subcutaneous Insulin Doses

Base your total daily dose on the average IV insulin infusion rate from the 12 hours prior to transition:

• Total daily dose = Average hourly IV insulin rate × 24 hours 3
• For example: If receiving 1.5 units/hour IV, total daily dose = 36 units 3
• Alternatively, start at 0.5-0.65 units/kg/day (approximately 40-50 units for a 77 kg patient) 1, 4

Divide the total daily dose:

• 50% as basal insulin (long-acting: glargine or detemir) given once daily 3
• 50% as prandial insulin (rapid-acting: lispro, aspart, or glulisine) divided equally before three meals 3

Specific Transition Protocol

Step 1: Administer basal insulin first

• Give glargine 40-50 units subcutaneously (or half the calculated total daily dose) 1, 4
• Timing is critical: 2-4 hours BEFORE stopping IV insulin 1, 2

Step 2: Continue IV insulin during overlap period

• Maintain IV insulin infusion for 1-2 hours after subcutaneous basal insulin administration 2
• This overlap prevents the gap in insulin coverage that causes rebound ketoacidosis 1, 2

Step 3: Initiate prandial insulin with meals

• Start rapid-acting insulin analog (lispro, aspart, or glulisine) before each meal 1, 2, 5
• Use 1:10 carbohydrate ratio (1 unit per 10 grams of carbohydrates) 1, 4
• Typical meal dose: 5-8 units before breakfast, lunch, and dinner 4

Step 4: Add correction scale

• Use 1 unit of rapid-acting insulin to lower glucose by 50 mg/dL 1, 4
• Target glucose: 100-150 mg/dL 1, 4
• Correction formula: (Current glucose - Target glucose) ÷ 50 1

Superior Regimen: Basal-Bolus with Analogs

A basal-bolus regimen using glargine and rapid-acting analogs (lispro, aspart, or glulisine) is superior to NPH and regular insulin after DKA resolution:

• Lower hypoglycemia rates: 15% with glargine/glulisine versus 41% with NPH/regular insulin (P = 0.03) 5
• Similar glycemic control but significantly safer 5
• Fewer hypoglycemic episodes: 8 events versus 26 events 5

Critical Pitfalls to Avoid

Never stop IV insulin before administering subcutaneous basal insulin — this is the most common error causing rebound hyperglycemia and recurrent DKA 1, 2

Never use sliding scale (correction-only) insulin alone — this approach leads to worse outcomes and higher complication rates in patients with known diabetes 3, 1

Never restart SGLT2 inhibitors during acute illness or until metabolically stable — these medications increase risk of recurrent DKA 1

Avoid NPH and regular insulin regimens when analogs are available — they cause significantly more hypoglycemia without improved efficacy 5

Monitoring After Transition

• Check glucose every 2-4 hours initially after transition 2
• Titrate basal insulin by 2-4 units every 3 days if fasting glucose >130 mg/dL 4
• Adjust carbohydrate ratios if postprandial glucose consistently >180 mg/dL 4
• Monitor potassium closely as hypoglycemia risk remains elevated during the first 24-48 hours 3, 1