What is the recommended insulin regimen for a patient with uncontrolled diabetes and significant obesity, specifically regarding the use of basal insulin (e.g. glargine (insulin glargine)) and short-acting insulin (e.g. aspart (insulin aspart) or lispro (insulin lispro))?

Insulin Regimen for 50-Year-Old Female with Uncontrolled Diabetes and Obesity (323 lbs)

Start with basal insulin glargine at 29-59 units once daily (0.1-0.2 units/kg based on her weight of ~147 kg), combined with metformin, and titrate upward by 10-15% (or 2-4 units) once or twice weekly until fasting glucose is controlled. 1

Initial Basal Insulin Dosing

• Calculate starting dose: For a patient weighing 323 lbs (147 kg), initiate insulin glargine at 15-29 units daily using the conservative 0.1 units/kg calculation, or up to 29-59 units using 0.2 units/kg if hyperglycemia is severe 1
• Alternative simplified approach: Start with a flat 10 units daily if you prefer a more cautious initiation 1
• Ensure metformin continuation: Basal insulin should be used with metformin (unless contraindicated) and possibly one additional oral agent 1

Titration Protocol

• Increase dose systematically: Adjust insulin glargine by 10-15% of the current dose, or by 2-4 units, once or twice weekly based on fasting blood glucose readings 1
• Target fasting glucose: Titrate until fasting blood glucose reaches <5.5-6.0 mmol/L (100-110 mg/dL) 1
• Empower patient self-titration: Provide the patient with a self-titration algorithm based on home glucose monitoring, which improves glycemic control 1

When to Add Rapid-Acting Insulin (Sliding Scale)

Only add prandial insulin if basal insulin has been optimally titrated (fasting glucose at goal) but HbA1c remains above target, or if basal dose exceeds 0.5 units/kg/day without achieving control. 1

Starting Prandial Insulin Doses

• Initial mealtime dose: Begin with 4 units per meal, OR 0.1 units/kg per meal, OR 10% of the basal insulin dose per meal 1
• Reduce basal when adding prandial: Consider decreasing basal insulin by the same amount as the starting mealtime dose to prevent excessive total daily insulin 1
• Preferred agents: Use rapid-acting insulin analogs (lispro, aspart, or glulisine) administered immediately before meals 1

Correction (Sliding Scale) Insulin Dosing

For this obese, insulin-resistant patient, use the insulin-resistant scale (standard doses increased by 50-100%): 2

• Blood glucose 5.5-8.3 mmol/L (100-150 mg/dL): 3-4 units rapid insulin 2
• Blood glucose 8.4-11.1 mmol/L (151-200 mg/dL): 6-8 units rapid insulin 2
• Blood glucose 11.2-13.9 mmol/L (201-250 mg/dL): 9-12 units rapid insulin 2
• Blood glucose 14.0-16.7 mmol/L (251-300 mg/dL): 12-16 units rapid insulin 2
• Blood glucose 16.8-19.4 mmol/L (301-350 mg/dL): 15-20 units rapid insulin 2
• Blood glucose >19.4 mmol/L (>350 mg/dL): 18-24 units rapid insulin and contact physician 2

Critical Sliding Scale Considerations

• Never use sliding scale alone: Correction insulin should always be combined with basal insulin (glargine); using sliding scale without basal insulin leads to suboptimal control 2
• Administer every 4-6 hours: Check glucose and give correction doses at this interval 2
• Avoid bedtime dosing: Do not give rapid insulin at bedtime to prevent nocturnal hypoglycemia 2

Special Considerations for Obesity

• Consider concentrated insulin formulations: If total daily insulin requirements exceed 200 units/day, U-500 regular insulin or U-300 glargine may be more appropriate and comfortable for injection 1
• Weight-neutral approach: Starting with basal insulin alone (rather than premixed or multiple daily injections initially) minimizes weight gain 3
• Monitor for insulin resistance: This patient will likely require higher doses due to obesity-related insulin resistance; don't hesitate to escalate doses appropriately 2, 4

Hypoglycemia Monitoring

• Primary safety concern: Close monitoring for hypoglycemia is essential, as it is the main adverse effect of insulin therapy 2
• Higher risk with intensive regimens: Adding prandial insulin to basal insulin increases hypoglycemia risk 4-6 fold compared to basal insulin alone 2
• Patient education mandatory: Comprehensive education on glucose monitoring, hypoglycemia recognition and treatment, insulin injection technique, and "sick day" rules is imperative 1

Alternative Considerations

• GLP-1 receptor agonist option: If basal insulin is optimized but HbA1c remains elevated, adding a GLP-1 receptor agonist instead of prandial insulin may provide better weight outcomes with less hypoglycemia, though at higher cost 1
• Premixed insulin alternative: Twice-daily premixed insulin (70/30 aspart or 75/25 lispro) is simpler but requires fixed meal schedules and may be suboptimal for postprandial control 1