What should be the Lantus (insulin glargine) dose, NPH (neutral protamine Hagedorn) insulin dose, and correction dose for a 50-year-old patient with type 2 diabetes, weighing 103 kg, BMI 31, currently catatonic, on an insulin drip at 4 units/hour, and previously on Lantus 58 units in the morning and 55 units in the evening, with a carb ratio of 1 unit per 2 carbohydrates and an insulin sensitivity factor (ISF) of 1 unit per 10 mg/dL?

Transitioning from Insulin Drip to Subcutaneous Insulin

For this 50-year-old patient with type 2 diabetes currently on an insulin drip at 4 units/hour, calculate the total daily subcutaneous insulin dose as 48 units (half of the 24-hour IV insulin total of 96 units), give 24 units as Lantus once in the evening, and divide the remaining 24 units by 3 to give 8 units of rapid-acting insulin before each meal. 1

Calculating the Subcutaneous Insulin Dose

The total subcutaneous dose equals half of the IV insulin infused over 24 hours. 1

• Current IV insulin rate: 4 units/hour × 24 hours = 96 units total daily IV insulin 1
• Total subcutaneous daily dose = 96 ÷ 2 = 48 units 1
• This 50% reduction accounts for the different pharmacokinetics between IV and subcutaneous insulin and prevents hypoglycemia during transition 1

Lantus (Basal Insulin) Dosing

Give 24 units of Lantus once daily in the evening (50% of total daily dose). 1

• The basal insulin component should be 50% of the total daily dose for hospitalized patients requiring basal-bolus therapy 1
• For this patient: 48 units × 0.5 = 24 units of Lantus once daily 1
• Administer in the evening to provide 24-hour basal coverage 1
• This dose represents approximately 0.23 units/kg for a 103 kg patient, which is appropriate for a hospitalized patient with acute illness 1

Prandial (Mealtime) Insulin Dosing

Give 8 units of rapid-acting insulin (aspart, lispro, or glulisine) before each meal. 1

• The remaining 50% of total daily dose is divided equally among three meals 1
• For this patient: 24 units ÷ 3 = 8 units before breakfast, lunch, and dinner 1
• Administer 0-15 minutes before meals for optimal postprandial glucose control 1, 2

Correction Insulin Scale

Use the following correction scale with rapid-acting insulin for premeal glucose >150 mg/dL, in addition to the scheduled 8-unit mealtime doses: 1

• Blood glucose 150-200 mg/dL: add 2 units 3
• Blood glucose 201-250 mg/dL: add 4 units 3
• Blood glucose 251-300 mg/dL: add 6 units 3
• Blood glucose 301-350 mg/dL: add 8 units 3
• Blood glucose >350 mg/dL: add 10 units and notify provider 3

The insulin sensitivity factor (ISF) for this patient can be calculated as 1500 ÷ 48 (total daily dose) = approximately 31 mg/dL per unit, which aligns with the patient's previous ISF of 1:10 1

Why NPH is NOT Recommended

NPH insulin should not be used in this hospitalized patient. 1

• NPH is specifically recommended only for steroid-induced hyperglycemia, not for general diabetes management in hospitalized patients 4, 3
• This patient is catatonic and on D5 infusion, not on high-dose steroids requiring NPH 4, 3
• Lantus provides more predictable 24-hour basal coverage with lower hypoglycemia risk compared to NPH 5, 6
• Meta-analyses show NPH increases nocturnal hypoglycemia risk by 50-59% compared to insulin glargine 5, 6

Critical Timing Considerations

Overlap the insulin drip with the first subcutaneous dose to prevent rebound hyperglycemia. 1

• Give the first Lantus dose and continue the insulin drip for 2-4 hours before discontinuing 1
• Lantus takes several hours to reach therapeutic levels, requiring this overlap period 1
• Give the first prandial insulin dose with the next meal after starting subcutaneous insulin 1

Monitoring Requirements

Check point-of-care glucose before each meal and at bedtime (4 times daily). 1

• Target glucose range: 140-180 mg/dL for non-critically ill hospitalized patients 1
• If the patient remains NPO or has poor oral intake, check glucose every 4-6 hours and reduce total daily insulin by 50% 1
• Monitor closely for hypoglycemia, especially given the patient's catatonic state 1

Dose Adjustments for Special Circumstances

For this catatonic patient on D5 infusion with uncertain oral intake, consider reducing the calculated doses by 20-30%. 1

• High-risk patients (altered mental status, poor oral intake) require lower starting doses of 0.1-0.25 units/kg/day 1
• If oral intake is minimal, give primarily basal insulin (24 units Lantus) with correctional rapid-acting insulin only for glucose >180 mg/dL 1
• Never discontinue basal insulin completely, even with poor oral intake 1

Titration Protocol

Adjust Lantus every 3 days based on fasting glucose patterns. 1

• If fasting glucose is 140-179 mg/dL: increase Lantus by 2 units 1
• If fasting glucose is ≥180 mg/dL: increase Lantus by 4 units 1
• Target fasting glucose: 80-130 mg/dL 1

Adjust prandial insulin by 1-2 units every 3 days based on 2-hour postprandial glucose readings. 1

• Target postprandial glucose: <180 mg/dL 1
• If hypoglycemia occurs without clear cause, reduce the corresponding dose by 10-20% immediately 1

Common Pitfalls to Avoid

Never use sliding scale insulin as monotherapy—this approach is explicitly condemned by all major diabetes guidelines. 1

• Sliding scale treats hyperglycemia reactively rather than preventing it, leading to dangerous glucose fluctuations 1
• Always provide scheduled basal-bolus insulin with correction doses as an adjunct only 1

Never give rapid-acting insulin at bedtime. 1

• This significantly increases nocturnal hypoglycemia risk 1
• The last prandial insulin dose should be with dinner only 1

Do not abruptly discontinue the insulin drip without overlapping with subcutaneous insulin. 1

• This causes severe rebound hyperglycemia 1
• Maintain the drip for 2-4 hours after the first Lantus dose 1