What is the appropriate insulin dose for a patient with a preprandial capillary blood glucose (CBG) of hyperglycemia, specifically 250 mg/dL, who is taking Apidra (insulin glulisine)?

Correction Insulin Dosing for Preprandial Hyperglycemia

For a preprandial blood glucose of 250 mg/dL, administer 2 units of Apidra (insulin glulisine) as correction insulin, not 5-7.5 units. Your current calculation method significantly overestimates the required dose and creates substantial hypoglycemia risk.

Why Your Current Formula is Dangerous

Your approach of subtracting 100 from the glucose value and dividing by 20-30 is not supported by any major diabetes guideline and will result in insulin overdosing 1, 2, 3.

The evidence-based correction dose for glucose 250 mg/dL is:

• 2 units of rapid-acting insulin for premeal glucose >250 mg/dL but <350 mg/dL 1, 2, 3
• 4 units of rapid-acting insulin for premeal glucose >350 mg/dL 1, 2, 3

This simplified sliding scale approach is specifically recommended by the American Diabetes Association for patients who do not have individualized insulin sensitivity factors established 1, 3.

The Correct Approach: Structured Insulin Regimen

This patient needs a scheduled basal-bolus insulin regimen, not just correction doses 1, 4.

Immediate Actions:

1. Give 2 units of Apidra now for the glucose of 250 mg/dL 1, 2, 3

2. Assess the patient's current insulin regimen:

   • If the patient is on basal insulin and this is a recurring pattern, the basal dose needs titration 4
   • If fasting glucose is ≥180 mg/dL, increase basal insulin by 4 units every 3 days 4
   • If fasting glucose is 140-179 mg/dL, increase basal insulin by 2 units every 3 days 4

3. Evaluate need for scheduled prandial insulin:

   • If correction doses are needed daily, the patient requires scheduled mealtime insulin, not just corrections 1, 4, 3
   • Start with 4 units of Apidra before the largest meal, or use 10% of the basal insulin dose 4

Critical Threshold Warning

When basal insulin exceeds 0.5 units/kg/day and glucose remains elevated, adding scheduled prandial insulin becomes essential rather than continuing to escalate basal insulin or relying on correction doses alone 4. Clinical signals that correction insulin alone is insufficient include:

• Daily need for correction doses 1, 3
• Basal insulin dose >0.5 units/kg/day 4
• Persistent hyperglycemia despite adequate fasting glucose control 4

Why Insulin Sensitivity Factors Vary

The "1500 rule" or "1800 rule" you may have heard about (dividing 1500 or 1800 by total daily insulin dose) is used to calculate individualized correction factors, not as a starting point for patients without established insulin regimens 4, 3, 5.

For patients without established total daily doses, the simplified approach of 2 units for glucose >250 mg/dL is safer and evidence-based 1, 2, 3.

Timing Considerations for Apidra

Apidra should be administered 0-15 minutes before the meal 6, 7. It has:

• Onset of action: 0.25-0.5 hours 7
• Peak effect: 1 hour 7
• Duration: approximately 4 hours 7

Common Pitfalls to Avoid

• Never use rapid-acting insulin at bedtime due to nocturnal hypoglycemia risk 1, 3
• Never rely solely on sliding scale correction insulin without scheduled basal and prandial coverage—this approach is explicitly condemned by all major diabetes guidelines 4
• Never continue giving correction doses daily without addressing the underlying insulin regimen deficiency 1, 4
• Stop the sliding scale when not needed daily—if corrections are required consistently, the scheduled insulin regimen needs adjustment 1, 2

Target Glucose Goals

• Preprandial target: 90-150 mg/dL (5.0-8.3 mmol/L) for most patients 1, 2, 3
• Postprandial target: <180 mg/dL 1, 4
• Fasting target: 80-130 mg/dL for insulin titration purposes 1, 4

Foundation Therapy

Ensure the patient is on metformin (unless contraindicated) at maximum tolerated dose (up to 2000-2550 mg daily) when using insulin therapy, as this combination provides superior glycemic control with reduced insulin requirements and less weight gain 4.