What is the recommended insulin regimen for a patient with diabetes who requires insulin therapy, using a combination of long-acting (e.g. glargine) and short-acting (e.g. aspart) insulin?

Recommended Insulin Regimen: Long-Acting and Short-Acting Insulin Combination

For patients with diabetes requiring insulin therapy, initiate basal insulin (glargine) at 10 units once daily or 0.1-0.2 units/kg body weight, administered at the same time each day, and add short-acting insulin (aspart) only when basal insulin has been optimized but glycemic targets remain unmet. 1, 2

Initial Approach: Start with Basal Insulin Alone

• Begin with insulin glargine (Lantus) as monotherapy at 10 units once daily or 0.1-0.2 units/kg/day for insulin-naive patients with type 2 diabetes 1, 2, 3
• Continue metformin at maximum tolerated dose (up to 2000-2550 mg daily) unless contraindicated, as this combination reduces insulin requirements and weight gain 1, 2
• Administer glargine subcutaneously into the abdominal area, thigh, or deltoid at the same time every day 3
• Do not mix or dilute glargine with any other insulin or solution due to its low pH 1, 3

Basal Insulin Titration Protocol

• Increase glargine by 2 units every 3 days if fasting glucose is 140-179 mg/dL 2
• Increase glargine by 4 units every 3 days if fasting glucose is ≥180 mg/dL 2
• Target fasting plasma glucose: 80-130 mg/dL 1, 2
• Reduce dose by 10-20% immediately if hypoglycemia occurs without clear cause 2
• Monitor fasting blood glucose daily during the titration phase 2

Critical Threshold: When to Add Short-Acting Insulin

Stop escalating basal insulin and add prandial coverage when:

• Basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day without achieving glycemic targets 1, 2
• Fasting glucose reaches target (80-130 mg/dL) but HbA1c remains above goal after 3-6 months 1, 2
• Clinical signs of "overbasalization" appear: bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia episodes, or high glucose variability 2

Adding Short-Acting Insulin (Aspart)

When basal insulin optimization is insufficient:

• Start with 4 units of insulin aspart before the largest meal, or use 10% of the current basal dose 2
• Administer aspart 0-15 minutes before meals for optimal postprandial glucose control 1, 4
• Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on 2-hour postprandial glucose readings 2
• Target postprandial glucose <180 mg/dL 2
• Gradually add aspart to additional meals if needed, based on glucose patterns 2

Type 1 Diabetes: Different Starting Approach

For type 1 diabetes, basal-bolus therapy is required from the outset:

• Total daily insulin dose: 0.4-1.0 units/kg/day (typically 0.5 units/kg/day for metabolically stable patients) 1, 2
• Divide as 40-60% basal insulin (glargine) and 40-60% prandial insulin (aspart) 1, 2
• Glargine must be used concomitantly with short-acting insulin in type 1 diabetes 3

Severe Hyperglycemia: Immediate Basal-Bolus Therapy

For patients with HbA1c ≥10-12% with symptomatic or catabolic features:

• Start basal-bolus insulin immediately rather than basal insulin alone 1, 2
• Total daily dose: 0.3-0.5 units/kg/day, divided 50% basal and 50% prandial 2

Mixing Insulin: Critical Restrictions

• Insulin glargine should NOT be mixed with other forms of insulin due to its low pH diluent 1, 3
• Rapid-acting insulin (aspart) can be mixed with NPH, lente, and ultralente if needed 1
• When rapid-acting insulin is mixed with intermediate- or long-acting insulin, inject within 15 minutes before a meal 1

Common Pitfalls to Avoid

• Never delay insulin initiation in patients not achieving glycemic goals with oral medications, as this prolongs hyperglycemia exposure 2
• Never continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia—this causes overbasalization with increased hypoglycemia risk 2
• Never discontinue metformin when starting insulin unless contraindicated, as this leads to higher insulin requirements and more weight gain 2
• Never use sliding scale insulin as monotherapy—scheduled basal-bolus regimens are superior 2, 5
• Never administer rapid-acting insulin at bedtime to avoid nocturnal hypoglycemia 2

Patient Education Requirements

• Proper insulin injection technique and site rotation to prevent lipodystrophy 1, 2
• Recognition and treatment of hypoglycemia with 15 grams of fast-acting carbohydrate 2
• Self-monitoring of blood glucose during titration and ongoing therapy 1, 2
• "Sick day" management rules and insulin storage/handling 1, 2

Monitoring Schedule

• Daily fasting blood glucose during active titration 2
• Pre-meal and 2-hour postprandial glucose when on prandial insulin 2
• HbA1c every 3 months during intensive titration 2
• Reassess therapy every 3-6 months once stable to avoid therapeutic inertia 2