What is the best insulin regimen for a patient with type 2 diabetes mellitus (T2DM)?

Best Insulin Regimen for Type 2 Diabetes

Start with basal insulin alone—specifically long-acting analogs like glargine, detemir, or degludec at 10 units once daily (or 0.1-0.2 units/kg/day)—added to metformin, and titrate aggressively every 3 days until fasting glucose reaches 80-130 mg/dL. 1, 2, 3

Initial Insulin Regimen: Basal Insulin First

Basal insulin is the most convenient and effective starting point for insulin therapy in type 2 diabetes 1, 2. This approach works by restraining hepatic glucose production overnight and between meals 1.

Specific starting protocol:

• Dose: 10 units once daily OR 0.1-0.2 units/kg body weight 1, 2, 3
• Timing: Same time each day (bedtime or morning) 2, 3
• Continue metformin unless contraindicated—this combination reduces insulin requirements and weight gain 1, 2, 3, 4

Preferred basal insulin products:

• Long-acting analogs (glargine U-100, detemir, degludec) cause less nocturnal hypoglycemia than NPH insulin 1, 3, 5
• Ultra-long analogs (glargine U-300, degludec U-200) may provide even lower hypoglycemia risk 1

Aggressive Titration Algorithm

Titrate every 3 days based on fasting glucose: 1, 2, 6

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

Daily fasting glucose monitoring is essential during titration 1, 2, 3. Most patients can self-titrate using this algorithm, which achieves better glycemic control than clinic-managed titration 6.

When to Advance Beyond Basal Insulin

Critical threshold—stop escalating basal insulin when dose exceeds 0.5 units/kg/day. 1, 2, 3 At this point, add prandial insulin or a GLP-1 receptor agonist rather than continuing to increase basal insulin 1, 2.

Clinical signals of "overbasalization" requiring advancement: 1, 2

• Basal dose >0.5 units/kg/day
• Bedtime-to-morning glucose differential ≥50 mg/dL
• Hypoglycemia episodes
• High glucose variability
• HbA1c remains above target after 3-6 months despite controlled fasting glucose

Adding Prandial Insulin

When basal insulin is optimized but HbA1c remains elevated, add rapid-acting insulin before meals: 1, 2, 3

Starting protocol:

• Begin with 4 units of rapid-acting insulin (lispro, aspart, or glulisine) before the largest meal 1, 2, 3
• Alternative: use 10% of current basal dose 1, 2
• Titrate by 1-2 units every 3 days based on 2-hour postprandial glucose 1, 2
• Add to additional meals if needed 1

Rapid-acting analogs provide better postprandial control than regular insulin 2, 3, 7.

Alternative: GLP-1 Receptor Agonist Instead of Prandial Insulin

Consider adding a GLP-1 RA to basal insulin rather than prandial insulin—this provides comparable HbA1c reduction with weight loss instead of weight gain and less hypoglycemia. 1, 2, 3 Fixed-ratio combinations (insulin glargine/lixisenatide or insulin degludec/liraglutide) are available 3.

Severe Hyperglycemia: Start with Basal-Bolus Immediately

For patients with HbA1c ≥10% or blood glucose ≥300-350 mg/dL with symptoms, skip basal-only and start basal-bolus insulin immediately 1, 2, 4:

• Total daily dose: 0.3-0.5 units/kg/day 1, 2
• Split 50% basal, 50% prandial (divided among three meals) 1, 2

Specialized Insulin Products

U-500 regular insulin: For patients requiring >200 units/day 1, 2

Inhaled insulin: Available for prandial use but contraindicated in chronic lung disease (asthma, COPD); requires spirometry screening 1, 2

Foundation Therapy: Never Stop Metformin

Continue metformin at maximum tolerated dose (up to 2000-2550 mg daily) when adding insulin. 1, 2, 3, 4 This combination provides superior glycemic control with reduced insulin requirements and less weight gain compared to insulin alone 4.

Discontinue sulfonylureas when advancing beyond basal-only insulin to prevent hypoglycemia 1, 2.

Critical Patient Education Requirements

Comprehensive education is imperative and must cover 1, 2, 4:

• Self-monitoring of blood glucose technique
• Insulin injection technique and site rotation (use 4-6mm needles) 4
• Recognition and treatment of hypoglycemia (15g fast-acting carbohydrate for glucose ≤70 mg/dL) 2
• "Sick day" management rules
• Insulin storage and handling
• Dietary and exercise modifications

Common Pitfalls to Avoid

Do not delay insulin initiation in patients not achieving glycemic goals with oral medications—this prolongs hyperglycemia exposure and increases complication risk 1, 2

Do not undertitrate insulin—aggressive dose adjustment every 3 days is essential 1, 2, 6

Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without adding prandial coverage—this causes overbasalization with hypoglycemia and suboptimal control 1, 2

Do not use sliding scale insulin as monotherapy—this is explicitly condemned by all major guidelines and leads to dangerous glucose fluctuations 2, 3

Do not abruptly discontinue oral medications when starting insulin—continue metformin unless contraindicated 2, 4