How to initiate insulin therapy in a patient with type 2 diabetes mellitus?

Initiating Insulin Therapy in Type 2 Diabetes

Basal insulin alone is the most convenient initial insulin regimen for type 2 diabetes, starting at 10 units or 0.1-0.2 units/kg/day, depending on the degree of hyperglycemia, with individualized titration over days to weeks. 1

When to Start Insulin Therapy

Insulin therapy should be considered in the following scenarios:

• When A1C is ≥9% 1
• When blood glucose is ≥300-350 mg/dL (16.7-19.4 mmol/L) or A1C ≥10-12%, especially with symptoms 1
• When oral medications fail to achieve glycemic targets 1
• During acute illness, surgery, or pregnancy 2
• When glucose toxicity is present 2

Initial Insulin Selection and Dosing

Step 1: Choose the Right Insulin Type

• Basal insulin is the preferred initial choice:
  • Long-acting analogs (glargine, detemir, degludec)
  • NPH insulin (more affordable but higher hypoglycemia risk) 1

Step 2: Calculate Starting Dose

• Starting dose: 10 units/day or 0.1-0.2 units/kg/day 1, 3
• For example:
  • 70 kg patient: 7-14 units (0.1-0.2 × 70)
  • Higher starting doses may be needed with severe hyperglycemia 1

Step 3: Timing of Administration

• Once-daily basal insulin should be administered with the evening meal or at bedtime 4
• If twice-daily dosing is required, the evening dose can be administered either with dinner, at bedtime, or 12 hours after the morning dose 4

Titration Protocol

Step 4: Implement a Structured Titration Plan

• Patient self-titration improves glycemic control 1
• Simple titration algorithm:
  • Adjust dose every 3-4 days based on fasting blood glucose (FBG) 5
  • If FBG >130 mg/dL for 3 consecutive days with no hypoglycemia, increase by 2 units 1, 6
  • If FBG 110-130 mg/dL, maintain current dose
  • If FBG <80 mg/dL or hypoglycemia occurs, reduce by 2-4 units 1

Step 5: Set Clear Glycemic Targets

• Fasting and premeal glucose: 80-130 mg/dL
• 2-hour postprandial glucose: <180 mg/dL 5
• A1C target: typically <7% (individualized based on patient factors) 1

Concomitant Medications

• Continue metformin when initiating insulin therapy 1
• Consider continuing or adding SGLT2 inhibitors to reduce insulin requirements 1
• Sulfonylureas, DPP-4 inhibitors, and GLP-1 receptor agonists are typically discontinued when complex insulin regimens beyond basal are used 1

Intensification of Insulin Therapy

If basal insulin has been titrated to an acceptable fasting glucose but A1C remains above target, consider:

1. Adding a GLP-1 receptor agonist (associated with weight loss and less hypoglycemia) 1
2. Adding mealtime (bolus) insulin before the largest meal:
   • Start with 4 units or 10% of basal dose 1
   • Rapid-acting analogs (lispro, aspart, glulisine) administered just before eating 1
3. Switching to twice-daily premixed insulin (e.g., 70/30 NPH/regular) 1

Monitoring and Education

• Self-monitoring of blood glucose is essential for insulin titration 1
• Comprehensive education on:
  • Injection technique and site rotation
  • Recognition and treatment of hypoglycemia
  • Diet and exercise adjustments
  • Sick day management 1

Potential Pitfalls and Caveats

• Overbasalization: Continuing to increase basal insulin beyond 0.5 units/kg/day without improvement in fasting glucose suggests the need for prandial coverage 1, 3
• Hypoglycemia risk: Higher with NPH compared to long-acting analogs 1
• Weight gain: Common with insulin initiation; combining with metformin may minimize this effect 1
• Patient resistance: Explain the progressive nature of type 2 diabetes and avoid framing insulin as a punishment or failure 1
• Injection site lipohypertrophy: Teach proper rotation of injection sites 7

By following this structured approach to insulin initiation and titration, patients with type 2 diabetes can achieve improved glycemic control with minimal risk of hypoglycemia, leading to better long-term outcomes in terms of morbidity and mortality.