When is insulin therapy recommended for patients with diabetes and how is it managed?

Insulin Therapy for Diabetes: Indications and Management

Insulin therapy is recommended for all patients with type 1 diabetes and for type 2 diabetes patients who have markedly symptomatic hyperglycemia, HbA1c ≥9%, blood glucose ≥300 mg/dL, or who fail to achieve glycemic targets with other medications. 1

Type 1 Diabetes Insulin Management

Recommended Therapy

• Multiple daily injections (MDI) (3-4 injections per day) or continuous subcutaneous insulin infusion (CSII/insulin pump) 1
• Typically includes:
  • Basal insulin: Long-acting insulin (glargine, detemir, degludec)
  • Bolus insulin: Rapid-acting insulin (lispro, aspart, glulisine) before meals

Dosing Guidelines

• Match prandial insulin to:
  • Carbohydrate intake
  • Pre-meal blood glucose levels
  • Anticipated physical activity 1
• Insulin analogs are preferred over human insulin due to less postprandial hyperglycemia and delayed hypoglycemia 2

Type 2 Diabetes Insulin Management

Indications for Insulin

1. At diagnosis when:

   • HbA1c ≥9% 1
   • Blood glucose ≥300-350 mg/dL 1
   • HbA1c ≥10-12% with symptomatic hyperglycemia 1
   • Presence of catabolic features or ketonuria 1

2. During disease progression:

   • When oral medications at maximum tolerated doses fail to achieve HbA1c targets over 3-6 months 1
   • During acute illness, surgery, or pregnancy 3
   • When glucose toxicity is present 3

Initial Insulin Regimen for Type 2 Diabetes

• Start with basal insulin at 10 units or 0.1-0.2 units/kg once daily, typically with metformin 1
• Initial dose for insulin-naïve patients: 0.2 units/kg or up to 10 units once daily 4
• Administer at the same time each day 4
• Titrate dose every 3 days based on fasting glucose levels 5:
  • FBG ≥180 mg/dL: Increase by 6-8 units
  • FBG 140-179 mg/dL: Increase by 4 units
  • FBG 120-139 mg/dL: Increase by 2 units
  • FBG <100 mg/dL: Decrease by 2-4 units
  • Any hypoglycemia (<70 mg/dL): Decrease by 10-20%

Intensification of Insulin Therapy

When basal insulin alone doesn't achieve target HbA1c:

1. Add prandial insulin (basal-bolus regimen):

   • Start with one mealtime injection (usually largest meal)
   • Initial dose: 4 units or 10% of basal dose 5
   • Adjust based on post-meal glucose readings

2. Consider premixed insulin 2-3 times daily 1

3. Alternative: Add GLP-1 receptor agonist to basal insulin 6, 7

   • May improve glycemic control with less weight gain and hypoglycemia

Insulin Administration Guidelines

Injection Technique

• Use shortest needles (4-mm pen, 6-mm syringe) 2
• Inject subcutaneously into abdomen, thigh, or deltoid 4
• Rotate injection sites to prevent lipohypertrophy 4, 2
• Never share insulin pens, needles, or syringes between patients 4

Monitoring and Adjustments

• Monitor blood glucose regularly:
  • Use fasting glucose to titrate basal insulin
  • Use both fasting and postprandial glucose to titrate mealtime insulin 2
• Increase monitoring frequency during regimen changes 4
• Target glucose levels:
  • Fasting/pre-meal: 80-130 mg/dL
  • Post-meal peak: 100-180 mg/dL 1

Special Considerations

Hospital Management

• For critically ill patients: IV insulin infusion with target glucose 140-180 mg/dL 1
• For non-critically ill patients: Basal-bolus regimen preferred over sliding scale insulin alone 1
• When transitioning from IV to subcutaneous insulin: Start subcutaneous insulin 1-2 hours before stopping IV infusion 1

Hypoglycemia Prevention

• Common triggers for hypoglycemia in hospitalized patients:
  • Sudden reduction of corticosteroid dose
  • Reduced oral intake or NPO status
  • Inappropriate timing of insulin relative to meals
  • Unexpected interruption of enteral/parenteral nutrition 1
• Always have a standardized hypoglycemia treatment protocol in place 1

Avoiding Common Pitfalls

1. Therapeutic inertia: Delaying insulin initiation despite persistent hyperglycemia 7
2. Overbasalization: Using excessive basal insulin when prandial coverage is needed 5
3. Relying solely on sliding scale insulin: This approach is strongly discouraged 1
4. Abrupt discontinuation of oral medications when starting insulin therapy 2

Remember that insulin requirements often change over time due to the progressive nature of type 2 diabetes, requiring regular reassessment and adjustment of therapy 1, 7.