What is the recommended Lantus dose, carb ratio, and correction scale for a 65-year-old male with type 2 diabetes, infected foot ulcer, and DKA?

Insulin Dosing for Type 2 Diabetes with DKA and Infected Foot Ulcer

Immediate DKA Management

This patient requires immediate IV insulin infusion at 0.1 units/kg/hour (approximately 7-8 units/hour for 77 kg) to resolve the DKA before transitioning to subcutaneous Lantus. 1, 2

IV Insulin Protocol During DKA

• Start continuous IV regular insulin at 0.1 units/kg/hour = 7.7 units/hour (round to 7-8 units/hour) 1, 2
• Do NOT use Lantus during active DKA - it is not indicated for DKA treatment 3
• Monitor blood glucose every 1-2 hours; expect glucose to fall 50-75 mg/dL per hour 2
• When glucose reaches 250 mg/dL, reduce IV insulin to 0.05-0.1 units/kg/hour (4-8 units/hour) and add dextrose to IV fluids 2
• Continue IV insulin until DKA resolves: glucose <200 mg/dL, bicarbonate ≥18 mEq/L, pH >7.3, anion gap ≤12 mEq/L 2, 4

Critical Electrolyte Management

• Check potassium before starting insulin - if K+ <3.3 mEq/L, delay insulin and correct potassium first to prevent fatal arrhythmias 4
• Add 20-30 mEq potassium per liter IV fluid (2/3 KCl, 1/3 KPO4) once K+ is 3.3-5.5 mEq/L and urine output is adequate 1, 4
• Target serum potassium 4-5 mEq/L throughout treatment 4

Transition to Subcutaneous Lantus

Administer the first dose of subcutaneous Lantus 2-4 hours BEFORE stopping the IV insulin infusion to prevent rebound hyperglycemia and recurrent DKA. 1, 4

Initial Lantus Dosing After DKA Resolution

Start Lantus at 40-50 units once daily (0.5-0.65 units/kg for 77 kg weight). 5

• Begin with 40 units daily and titrate up to 50 units based on fasting glucose 5
• Administer at the same time each day (patient can choose morning or evening) 3
• This aggressive dosing is necessary given the recurrent DKA history and infected foot ulcer causing insulin resistance 5

Titration Schedule

• Increase Lantus by 2-4 units every 3 days if fasting glucose remains >130 mg/dL 5
• Monitor fasting glucose daily during titration 5

Prandial Insulin: Carbohydrate Ratio

Start with a 1:10 carbohydrate ratio using rapid-acting insulin (e.g., lispro, aspart) before each meal. 5

• 1 unit of rapid-acting insulin per 10 grams of carbohydrate 5
• For a typical meal with 50-80 grams of carbohydrates, this equals 5-8 units per meal 5
• Adjust the ratio every 2-3 days based on 2-hour postprandial glucose readings 5
• If postprandial glucose consistently >180 mg/dL, tighten ratio to 1:8 or 1:7 5

Correction Scale (Insulin Sensitivity Factor)

Use 1 unit of rapid-acting insulin to lower blood glucose by 50 mg/dL, with target glucose 100-150 mg/dL. 5

Correction Dose Calculation

• Correction dose = (Current glucose - Target glucose) ÷ 50 5
• Example: If glucose is 250 mg/dL and target is 120 mg/dL: (250-120) ÷ 50 = 2.6 units (round to 2-3 units)
• Administer correction doses with meals or every 4-6 hours if needed 5
• If corrections are consistently ineffective, tighten the correction factor to 1:40 (1 unit lowers glucose by 40 mg/dL) 5

Complete Daily Insulin Regimen Post-DKA

Total daily dose: approximately 80-100 units 5

Breakdown:

• Basal insulin (Lantus): 40-50 units once daily 5
• Prandial insulin: 30-50 units total, divided across 3 meals (approximately 10-17 units per meal depending on carbohydrate intake) 5
• Correction doses: as needed based on above scale 5

Special Considerations for This Patient

Infected Foot Ulcer Impact

• The infection significantly increases insulin resistance and requirements 6, 7
• Aggressive glucose control (target 100-180 mg/dL) improves wound healing and reduces infection spread 6
• Monitor inflammatory markers (CRP, WBC) alongside glucose control 6

Medication Adjustments

• Discontinue Jardiance (SGLT2 inhibitor) immediately - it should have been stopped 3-4 days before any acute illness to prevent DKA 1, 4
• Hold metformin during acute illness and restart once stable and eating normally 1
• Do not restart Jardiance until infection is resolved and patient is metabolically stable 1

Monitoring During Transition

• Check blood glucose before each meal and at bedtime (minimum 4 times daily) 5
• Draw electrolytes, glucose, and venous pH every 2-4 hours until DKA fully resolves 1, 2
• Monitor for hypoglycemia, especially during the first 48-72 hours after transition 1

Critical Pitfalls to Avoid

• Never stop IV insulin before administering subcutaneous basal insulin - this causes rebound hyperglycemia and recurrent DKA 1, 4
• Never use correction-only insulin without basal coverage - this approach leads to worse outcomes and higher complication rates 1
• Never restart SGLT2 inhibitors during acute illness or infection - risk of recurrent DKA 1, 4
• Never delay insulin therapy if potassium is adequate - early insulin administration speeds DKA resolution 8
• Rotate injection sites to prevent lipodystrophy, which causes erratic insulin absorption and hyperglycemia 3