How to calculate basal and bolus insulin regimen in a Diabetic Ketoacidosis (DKA) patient with a current Random Blood Sugar (RBS) of 124 mg/dL, initial RBS of 513 mg/dL, and total insulin given of 160 units?

Calculating Basal-Bolus Insulin Regimen After DKA Resolution

Administer basal insulin 2-4 hours before stopping IV insulin at 80% of the total insulin requirement over the last 6 hours, then divide the remaining 20% as prandial insulin across meals.

Calculating Your Patient's Insulin Requirements

Step 1: Determine Total Daily Dose (TDD)

• Your patient received 160 units total during DKA treatment 1
• Calculate the hourly insulin requirement during the last 6 hours of IV insulin infusion when glucose was stable 1
• Multiply this hourly rate by 24 to estimate TDD 1
• Example calculation: If the patient was receiving 5 units/hour in the final 6 hours → 5 × 24 = 120 units TDD

Step 2: Calculate Basal Insulin Dose

• Give 50% of TDD as basal insulin (long-acting analog like glargine or detemir) 1
• Using the example above: 120 units × 0.5 = 60 units of basal insulin daily 1
• Critical timing: Administer this basal insulin 2-4 hours before discontinuing IV insulin to prevent rebound hyperglycemia and recurrent ketoacidosis 1

Step 3: Calculate Prandial (Bolus) Insulin Dose

• Give 50% of TDD divided across three meals as rapid-acting insulin (lispro, aspart, or glulisine) 1
• Using the example: 120 units × 0.5 = 60 units total prandial ÷ 3 meals = 20 units per meal 1
• Alternatively, distribute based on meal size: 40% before breakfast, 30% before lunch, 30% before dinner 1

Step 4: Add Correction Scale

• Use the 1800 rule to calculate correction factor: 1800 ÷ TDD 2
• Example: 1800 ÷ 120 = correction factor of 15 (1 unit lowers glucose by ~15 mg/dL) 2
• Target glucose 100-180 mg/dL in the post-DKA period 1, 2

Specific Regimen for Your Patient

Given current glucose of 124 mg/dL (near target), here's the practical approach:

Basal Insulin

• Calculate average hourly insulin rate from last 6 hours of IV infusion 1
• Multiply by 24, then take 50% for basal dose 1
• Administer 2-4 hours before stopping IV insulin 1

Prandial Insulin

• Take remaining 50% of calculated TDD 1
• Divide by 3 meals: approximately 15-20 units per meal for most patients transitioning from DKA 1
• Give before each meal with rapid-acting insulin 1

Correction Scale (Supplemental)

• Blood glucose 150-200 mg/dL: 2 units 2
• Blood glucose 201-250 mg/dL: 4 units 2
• Blood glucose 251-300 mg/dL: 6 units 2
• Blood glucose 301-350 mg/dL: 8 units 2
• Blood glucose >350 mg/dL: 10 units and notify provider 2

Critical Pitfalls to Avoid

Timing Errors

• Never stop IV insulin abruptly without prior subcutaneous basal insulin administration—this causes rebound hyperglycemia and recurrent DKA 1
• The 2-4 hour overlap is essential because subcutaneous basal insulin takes time to reach therapeutic levels 1

Dosing Errors

• Do not use the total 160 units given during acute DKA as your TDD—this represents crisis management, not maintenance needs 1
• Use only the stable hourly rate from the last 6 hours when glucose was controlled 1
• Recent evidence shows that adding low-dose basal insulin (0.2 units/kg) during IV insulin infusion prevents rebound hyperglycemia 1, 3

Monitoring Requirements

• Check glucose every 2-4 hours initially after transition 1
• Adjust doses by 10-20% if hypoglycemia occurs without clear cause 1, 2
• If A1C remains above goal after stabilization, consider adding GLP-1 receptor agonist to the regimen 1

Alternative Approach for Mild-Moderate DKA

Recent evidence supports using subcutaneous insulin from the start in uncomplicated DKA: single doses of glargine (0.2 units/kg) and lispro (0.2 units/kg) initially, followed by lispro (0.1-0.2 units/kg) every 3 hours until resolution 3. This approach achieved 90% DKA resolution within 12 hours with comparable safety to IV insulin 3.