What are the indications for starting insulin therapy in a patient with type 2 diabetes?

Indications for Starting Insulin in Type 2 Diabetes

Insulin therapy should be initiated in patients with type 2 diabetes when they have markedly symptomatic hyperglycemia, blood glucose ≥16.7-19.4 mmol/L (≥300-350 mg/dL), A1C ≥9-10%, or when oral agents fail to achieve glycemic targets within 3 months. 1

Primary Indications for Insulin Initiation

• Severe hyperglycemia at diagnosis:

  • A1C ≥9% with symptoms (polyuria, polydipsia, weight loss)
  • A1C ≥10% even without symptoms
  • Blood glucose ≥16.7-19.4 mmol/L (≥300-350 mg/dL)

• Failure of non-insulin therapies:

  • Persistent hyperglycemia despite optimized oral antidiabetic medications
  • When basal insulin has been titrated to an acceptable fasting blood glucose but A1C remains above target 2

• Special clinical situations:

  • Acute illness or surgery
  • Pregnancy
  • Glucose toxicity (where short-term intensive insulin may restore beta-cell function)
  • Contraindications to oral antidiabetic medications

Initial Insulin Regimen Selection

The choice of initial insulin regimen depends on the severity of hyperglycemia:

1. For severe hyperglycemia at diagnosis:

   • Basal insulin + mealtime insulin
   • Starting dose: 10 units or 0.1-0.2 units/kg 1

2. For less severe hyperglycemia:

   • Basal insulin alone (NPH, glargine, detemir, or degludec)
   • Starting dose: 10 units or 0.1-0.2 units/kg/day 2
   • Increase by 10-15% or 2-4 units once or twice weekly until fasting blood glucose target is met

3. Short-term intensive insulin therapy:

   • Consider for newly diagnosed patients with A1C >9.0%
   • May help reverse glucose toxicity and restore beta-cell function 3
   • Can potentially lead to remission in some patients

Insulin Intensification Algorithm

When basal insulin alone fails to achieve target A1C despite adequate fasting glucose control:

1. Add a GLP-1 receptor agonist (associated with weight loss and less hypoglycemia)

2. Add mealtime insulin:

   • Start with a single injection of rapid-acting insulin before largest meal
   • Initial dose: 4 units per meal, 0.1 units/kg per meal, or 10% of basal dose if A1C <8%
   • Consider reducing basal insulin by the same amount as the starting mealtime dose 2

3. Switch to premixed insulin twice daily (70/30 NPH/regular, 70/30 aspart, or 75/25 or 50/50 lispro mix)

4. Progress to basal-bolus regimen if targets still not achieved (basal insulin plus multiple daily injections of rapid-acting insulin)

Monitoring and Dose Adjustments

• Self-monitoring of blood glucose 3-4 times daily initially
• Adjust insulin doses every 3-4 days until targets reached
• Target fasting and premeal glucose: 4.4-7.2 mmol/L (80-130 mg/dL)
• Target 2-hour postprandial glucose: <10 mmol/L (<180 mg/dL)
• Assess A1C every 3 months to evaluate effectiveness

Common Pitfalls to Avoid

1. Delayed insulin initiation despite persistent hyperglycemia, which increases risk of complications 1

2. Discontinuing metformin when starting insulin - metformin should generally be continued to limit weight gain and insulin dose requirements

3. Inadequate dose titration - failure to adjust insulin doses systematically based on blood glucose patterns

4. Ignoring hypoglycemia risk - patients with history of severe hypoglycemia may need less stringent glycemic targets

5. Insufficient patient education - comprehensive education on insulin administration, blood glucose monitoring, diet, and hypoglycemia management is essential for successful insulin therapy

Remember that diabetes is a progressive condition, and many patients with type 2 diabetes eventually require insulin therapy. Early patient education about disease progression and avoiding threats of future insulin therapy can make the transition easier when needed 2.