What is the appropriate insulin regimen for a 42-year-old male with obesity (Body Mass Index (BMI) 31), hypertension (HTN), hyperlipidemia (HLD), type 2 diabetes mellitus (T2DM) with a significantly elevated hemoglobin A1c (HbA1c) of 10.4, impaired renal function (Creatinine (Cr) 1.13, Glomerular Filtration Rate (GFR) 83), and currently admitted to the hospital with a leg infection, who is nil per os (NPO) and not taking any medications after previously taking metformin, Mounjaro (tirzepatide), and glipizide?

Insulin Regimen for Hospitalized NPO Patient with Severe Hyperglycemia

Immediate Insulin Regimen

For this 87 kg patient with severe uncontrolled diabetes (A1c 10.4%) who is NPO, initiate basal insulin at 0.3-0.5 units/kg/day given the severity of hyperglycemia, which translates to 26-44 units of Lantus once daily, starting with approximately 35 units. 1, 2

Specific Dosing Recommendations

Basal Insulin (Lantus):

• Start with 35 units once daily (approximately 0.4 units/kg for 87 kg) 1
• For NPO patients, a basal-only regimen with correction insulin is preferred over basal-bolus 3
• Administer at the same time each day, typically evening 1

Correction Insulin:

• Use rapid-acting insulin (aspart or lispro) for correction doses only 3
• Simplified sliding scale: 2 units for glucose >250 mg/dL, 4 units for glucose >350 mg/dL 1
• Check point-of-care glucose every 4-6 hours given NPO status 1

Critical Renal Considerations

This patient has stage 3a chronic kidney disease (GFR 83, Cr 1.13), requiring dose adjustment. 1

• Reduce the calculated dose by approximately 20% to prevent hypoglycemia 1
• Therefore, start with 28-30 units of Lantus rather than 35 units 1
• Monitor closely for hypoglycemia as insulin clearance is impaired 1

Lantus Dose Titration Protocol

Titrate aggressively given the A1c of 10.4%: 1

• If fasting glucose ≥180 mg/dL: increase by 4 units every 3 days 1
• If fasting glucose 140-179 mg/dL: increase by 2 units every 3 days 1
• Target fasting glucose: 80-130 mg/dL 3, 1
• If hypoglycemia occurs (<70 mg/dL), reduce dose by 10-20% immediately 1

Critical threshold monitoring: 1

• When basal insulin approaches 0.5-1.0 units/kg/day (44-87 units), this signals overbasalization 1
• At this point, adding prandial insulin becomes more appropriate than continuing to escalate basal insulin alone 1

Carbohydrate Ratio (When Resuming Oral Intake)

Once the patient resumes eating, transition to basal-bolus therapy: 1

Initial Prandial Insulin:

• Start with 4 units of rapid-acting insulin before the largest meal 1
• Alternatively, use 10% of basal dose (approximately 3-4 units if on 30-40 units basal) 1

Carbohydrate-to-Insulin Ratio (ICR):

• Calculate using formula: 450 ÷ Total Daily Dose (TDD) for rapid-acting analogs 1
• For estimated TDD of 40 units: 450 ÷ 40 = 1 unit per 11 grams of carbohydrate 1
• Common starting ratio: 1 unit per 10-15 grams of carbohydrate 1

Insulin Sensitivity Factor (Correction Factor):

• Calculate using formula: 1500 ÷ TDD 1
• For TDD of 40 units: 1500 ÷ 40 = 1 unit lowers glucose by approximately 38 mg/dL 1

Transition Plan When Resuming Oral Intake

When NPO status is lifted: 3

• Continue basal insulin at current dose 3
• Add prandial insulin 0-15 minutes before meals 1
• Split total daily dose: approximately 50% basal, 50% prandial (divided among three meals) 1
• If on 40 units total: 20 units Lantus + 6-7 units rapid-acting before each meal 1

Monitoring Requirements

During NPO status: 1

• Check glucose every 4-6 hours 1
• Monitor for hypoglycemia, especially given renal impairment 1
• Assess adequacy of basal insulin based on fasting and between-meal glucose patterns 1

After resuming oral intake: 1

• Check fasting glucose daily to guide basal insulin titration 1
• Check pre-meal and 2-hour postprandial glucose to guide prandial insulin adjustments 1

Critical Pitfalls to Avoid

Never use sliding scale insulin as monotherapy - this approach is explicitly condemned by all major guidelines and leads to dangerous glucose fluctuations 3, 4

Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day (44-87 units for this patient) without addressing postprandial hyperglycemia, as this causes overbasalization with increased hypoglycemia risk 1

Do not give rapid-acting insulin at bedtime to avoid nocturnal hypoglycemia 1

Monitor potassium closely - ensure potassium >3.3 mEq/L before continuing insulin, especially given infection and potential fluid shifts 2

Adjust for infection-related insulin resistance - the purulent cellulitis may increase insulin requirements by 40-60% or more 1

Foundation Therapy Considerations

Once oral intake resumes, restart metformin (previously on metformin) unless contraindicated by acute illness or renal function deterioration 1

• Metformin combined with insulin reduces insulin requirements and weight gain 5
• Verify renal function stable (GFR >30 mL/min) before restarting 6

Discontinue glipizide permanently - sulfonylureas should be stopped when advancing to insulin therapy to prevent hypoglycemia 1, 7

Consider restarting Mounjaro (tirzepatide) after acute illness resolves, as GLP-1 RA combined with basal insulin provides superior outcomes with less hypoglycemia and weight gain 1