What are the guidelines for initiating and managing insulin therapy in patients with diabetes?

Guidelines for Initiating and Managing Insulin Therapy in Diabetes

Insulin therapy should be initiated when patients with type 2 diabetes have HbA1c ≥7.5% despite optimized oral agents, or immediately in those with HbA1c ≥10%, severe hyperglycemia causing ketosis, or unintentional weight loss. 1

Initial Insulin Selection and Dosing

Basal Insulin Initiation

• Starting dose:
  • Type 2 diabetes: 10 units/day or 0.1-0.2 units/kg/day 1, 2, 3
  • Type 1 diabetes: Approximately one-third of total daily insulin requirements 2
• Options for basal insulin:
  • Long-acting analogs: glargine, detemir, or degludec
  • Intermediate-acting: NPH insulin 1
• Advantages of long-acting analogs:
  • Lower risk of nocturnal hypoglycemia compared to NPH 4, 5
  • More stable glucose profile without pronounced peaks 4

Titration of Basal Insulin

• Adjust dose by 1-2 units every 2-3 days based on fasting blood glucose values 2, 3
• Target fasting glucose: 80-130 mg/dL 3
• Continue titration until target achieved or dose reaches approximately 0.5-1.0 units/kg/day 3

Progression of Insulin Therapy

When Basal Insulin Is Insufficient

When basal insulin has been optimized but HbA1c remains above target, consider:

1. Add GLP-1 receptor agonist 1

   • Provides complementary glucose-lowering with less hypoglycemia risk

2. Add prandial (bolus) insulin 1

   • Start with one injection at largest meal
   • Initial dose: 4 units or 10% of basal dose 6
   • Adjust based on pre- and post-meal glucose values

3. Switch to premixed insulin 1

   • Options: 70/30 NPH/regular, 70/30 aspart mix, 75/25 or 50/50 lispro mix
   • Typically administered twice daily (before breakfast and dinner)

Multiple Daily Injection (MDI) Regimen

• Total daily insulin typically divided as:
  • 40-50% basal insulin
  • 50-60% as bolus insulin 6, 7
• Bolus insulin dose calculation:
  • Corrective dose (based on current glucose)
  • Plus meal coverage dose (based on carbohydrate intake)

Special Considerations

Switching Between Insulin Types

• When switching from:
  • Insulin glargine 300 units/mL to glargine 100 units/mL: Use 80% of previous dose 2
  • Once-daily NPH to glargine: Use same dose 2
  • Twice-daily NPH to once-daily glargine: Use 80% of total NPH dose 2

Insulin in Type 1 Diabetes

• Always requires multiple daily injections at diagnosis 7
• Must include both basal and bolus components 7
• Never discontinue basal insulin, even during illness 1

Monitoring and Adjustment

• Use fasting glucose values to titrate basal insulin 7
• Use both fasting and postprandial values to titrate mealtime insulin 7
• Increase monitoring frequency during dose adjustments 2

Practical Administration Tips

• Rotate injection sites within same region to reduce risk of lipodystrophy 2
• Inject into abdomen, thigh, or deltoid 2
• Use shortest needles available (4-mm pen, 6-mm syringe) to avoid intramuscular injection 7
• Never share insulin pens, syringes, or needles between patients 2

Common Pitfalls to Avoid

1. Overbasalization: Continuing to increase basal insulin without improvement in fasting glucose; consider adding prandial insulin instead 3

2. Delayed intensification: Not advancing therapy when basal insulin alone is insufficient 1

3. Inadequate monitoring: Not checking glucose frequently enough during titration 2

4. Abrupt discontinuation: Never abruptly stop oral medications when starting insulin due to risk of rebound hyperglycemia 7

5. Ignoring hypoglycemia: Failing to adjust insulin doses when hypoglycemia occurs 1

By following these guidelines, clinicians can effectively initiate and manage insulin therapy to achieve optimal glycemic control while minimizing the risks of hypoglycemia and other adverse effects.