What is the appropriate Lantus (insulin glargine) dose, insulin-to-carbohydrate ratio (ICR), and insulin sensitivity factor (ISF) for an 82kg patient with a body mass index (BMI) of 24, impaired glycemic control (A1c 10.1), mild impaired renal function (creatinine 1.11, glomerular filtration rate (GFR) 71), and a 15-year history of type 2 diabetes, currently on Amaryl (glimepiride) 4mg twice daily, Metformin 1000mg twice daily, and Jardiance (empagliflozin) 25mg, presenting with gangrene of the foot?

Insulin Dosing for Hospitalized Patient with Gangrene and Uncontrolled Diabetes

Immediate Insulin Initiation: Basal-Bolus Regimen Required

For this 82kg patient with A1c 10.1%, 15-year diabetes duration, and acute foot gangrene requiring hospitalization, initiate basal-bolus insulin therapy immediately with Lantus 25-33 units once daily (0.3-0.4 units/kg/day as total daily dose, split 50% basal/50% prandial), insulin-to-carbohydrate ratio (ICR) of 1:10, and insulin sensitivity factor (ISF) of 30-40 mg/dL per unit. 1, 2, 3

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Lantus (Basal Insulin) Dose Calculation

Initial Dose: 25-33 Units Once Daily

• Start with 0.3-0.4 units/kg/day as total daily insulin dose given the severe hyperglycemia (A1c 10.1%) and acute illness with gangrene 2, 3
• For this 82kg patient: 0.3 × 82 = 24.6 units, or 0.4 × 82 = 32.8 units total daily dose 2
• Give 50% as basal insulin (Lantus): 12-16 units once daily 1, 2
• However, for hospitalized patients with severe hyperglycemia and acute illness, use the higher end: Start with 25-33 units Lantus once daily (approximately 0.3-0.4 units/kg/day) 2, 3

Critical Adjustments for Renal Impairment

• With GFR 71 ml/min (Stage 2 CKD), initiate conservatively at the lower end of dosing range to avoid hypoglycemia 1
• Reduce dose by 10-20% if hypoglycemia occurs 1, 2
• Start with 25 units Lantus once daily given renal function and acute illness 1, 2

Medication Adjustments Required

• STOP Amaryl (glimepiride) immediately - sulfonylureas significantly increase hypoglycemia risk when combined with insulin in hospitalized patients 1
• Continue Metformin 1000mg BID unless contraindicated by acute illness or declining renal function 4, 2
• Continue Jardiance 25mg - SGLT2 inhibitors provide cardiovascular and renal protection, but monitor closely for euglycemic DKA given insulin requirement and acute stress 1, 5
• Pause Jardiance temporarily if patient becomes NPO or develops signs of infection/sepsis to reduce DKA risk 1

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Prandial Insulin Dosing

Initial Prandial Dose: 12-16 Units Daily (Divided)

• Give remaining 50% of total daily dose as prandial insulin divided among three meals 1, 2
• For 25-33 units total daily dose: 4-5 units rapid-acting insulin (Humalog/NovoLog/Apidra) before each meal 1, 2
• Start with 4 units before each meal and adjust based on postprandial glucose readings 4, 2

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Insulin-to-Carbohydrate Ratio (ICR)

ICR = 1:10 (1 unit per 10 grams carbohydrate)

• Calculate using 500 Rule: 500 ÷ Total Daily Dose 2
• For 30 units total daily dose: 500 ÷ 30 = 16.7, round to 1:15-20 2
• However, for severe hyperglycemia (A1c 10.1%), start more aggressively with 1:10 2
• This means 1 unit of rapid-acting insulin covers 10 grams of carbohydrate 2

Practical Application

• If patient eats 60 grams carbohydrate at lunch: 60 ÷ 10 = 6 units rapid-acting insulin 2
• Adjust ICR by 1-2 units every 3 days based on 2-hour postprandial glucose readings 4, 2

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Insulin Sensitivity Factor (ISF)

ISF = 30-40 mg/dL per unit

• Calculate using 1500 Rule: 1500 ÷ Total Daily Dose 2
• For 30 units total daily dose: 1500 ÷ 30 = 50 mg/dL per unit 2
• For severe hyperglycemia and acute illness, use more aggressive ISF of 30-40 to correct hyperglycemia faster 2
• This means 1 unit of rapid-acting insulin lowers blood glucose by 30-40 mg/dL 2

Correction Dose Calculation

• Target glucose: 140 mg/dL (hospitalized patient target 140-180 mg/dL) 1
• If pre-meal glucose is 240 mg/dL: (240 - 140) ÷ 40 = 2.5 units correction dose 2
• Add correction dose to carbohydrate coverage dose 2

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Titration Protocol

Basal Insulin Adjustment (Every 3 Days)

• If fasting glucose ≥180 mg/dL: Increase Lantus by 4 units 2, 3
• If fasting glucose 140-179 mg/dL: Increase Lantus by 2 units 2, 3
• Target fasting glucose: 80-130 mg/dL (may accept 100-140 mg/dL in hospitalized elderly patient) 1, 2
• If fasting glucose <80 mg/dL on 2+ occasions: Decrease Lantus by 2 units 2

Prandial Insulin Adjustment (Every 3 Days)

• Adjust based on 2-hour postprandial glucose readings 4, 2
• If postprandial glucose >180 mg/dL: Increase prandial dose by 1-2 units 4, 2
• If postprandial glucose <100 mg/dL: Decrease prandial dose by 1-2 units 2

Critical Threshold Warning

• When Lantus exceeds 0.5 units/kg/day (41 units for 82kg patient), STOP escalating basal insulin 4, 2
• Instead, intensify prandial insulin coverage to avoid "overbasalization" 4, 2
• Signs of overbasalization: bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia, high glucose variability 4, 2

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Monitoring Requirements

Blood Glucose Testing Schedule

• Check fasting glucose daily to guide Lantus titration 1, 2
• Check pre-meal glucose before each meal (if eating) 1
• Check bedtime glucose to assess overnight basal coverage 1, 2
• Check every 6 hours minimum if NPO or poor oral intake 6

Laboratory Monitoring

• Daily creatinine and electrolytes given renal impairment and SGLT2 inhibitor use 1
• Monitor for ketones if glucose >250 mg/dL or patient develops nausea/vomiting (SGLT2i + insulin = DKA risk) 1
• Recheck A1c in 3 months after discharge 1, 2

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Special Considerations for Gangrene/Acute Illness

Stress Hyperglycemia Management

• Acute illness increases insulin requirements by 30-50% 6
• If patient develops sepsis or requires surgery, expect insulin needs to DOUBLE 6
• Reduce insulin by 20-30% immediately when acute illness resolves to prevent hypoglycemia 6

NPO/Poor Oral Intake Protocol

• If NPO: Give 100% of Lantus dose, HOLD all prandial insulin 1, 6
• Use correction doses only if patient actually eats 6
• Basal insulin represents 30-50% of total daily requirements and prevents ketosis 1, 6

Renal Function Deterioration

• If GFR drops below 45 ml/min: Reduce Metformin to 1000mg daily maximum 1
• If GFR drops below 30 ml/min: STOP Metformin 1
• Reduce insulin doses by 10-20% with declining renal function to prevent prolonged hypoglycemia 1

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Common Pitfalls to Avoid

Critical Errors in Hospitalized Patients

• DO NOT continue sliding-scale insulin monotherapy - this reactive approach leads to poor control and glucose variability 1
• DO NOT delay insulin intensification - this patient needs basal-bolus therapy NOW, not gradual titration 1, 2
• DO NOT continue Amaryl with insulin - sulfonylureas cause severe hypoglycemia in hospitalized patients 1
• DO NOT escalate Lantus beyond 0.5 units/kg/day without adding prandial insulin - this causes overbasalization 4, 2

SGLT2 Inhibitor Safety

• PAUSE Jardiance if patient becomes NPO, develops infection, or requires surgery 1
• Monitor for euglycemic DKA (ketones with glucose <250 mg/dL) - this is a medical emergency 1
• Maintain at least low-dose insulin when using SGLT2i to prevent DKA 1

Hypoglycemia Prevention

• Reduce insulin by 10-20% immediately if ANY hypoglycemia occurs 1, 2
• Elderly patients (this patient is likely >60 years given 15-year diabetes duration) require more conservative targets 1
• Accept fasting glucose 100-140 mg/dL in high-risk patients rather than aggressive 80-130 mg/dL target 1

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Discharge Planning

Transition to Outpatient Regimen

• Continue basal-bolus regimen at discharge - do NOT simplify to basal-only with A1c 10.1% 1, 2
• Provide self-titration algorithm for patient to adjust insulin at home 2, 3
• Schedule follow-up within 2-4 weeks to reassess regimen 4
• Restart or continue Jardiance for cardiovascular/renal protection once acute illness resolves 1, 5
• Continue Metformin unless contraindicated 4, 2