What are the basics of insulin therapy and best practices for initiating treatment in patients with diabetes?

Insulin Therapy Basics and Best Practices for Diabetes Management

Basal insulin alone is the most convenient initial insulin regimen for patients with type 2 diabetes, beginning at 10 units per day or 0.1-0.2 units/kg/day, depending on the degree of hyperglycemia. 1

Types of Insulin and Their Roles

Basal Insulin

• Purpose: Controls fasting blood glucose by restraining hepatic glucose production overnight and between meals 1
• Options:
  • Long-acting analogs: glargine, detemir, degludec
  • Intermediate-acting: NPH insulin
• Administration: Usually once daily, at same time each day
• Starting dose: 10 units or 0.1-0.2 units/kg/day 1
• Advantages of long-acting analogs: Lower risk of nocturnal hypoglycemia compared to NPH insulin 1

Bolus (Prandial) Insulin

• Purpose: Covers mealtime carbohydrates and corrects current glucose levels
• Options:
  • Rapid-acting analogs: lispro, aspart, glulisine (preferred due to faster onset) 1
  • Short-acting: regular insulin
• Starting dose: 4 units, 0.1 units/kg per meal, or 10% of basal dose 1
• Timing: Administered immediately before meals 1

Premixed Insulin

• Purpose: Provides both basal and prandial coverage in fixed proportions
• Options: 70/30 NPH/regular, 70/30 aspart mix, 75/25 or 50/50 lispro mix 1
• Administration: Usually twice daily (before breakfast and dinner)
• Limitation: Requires relatively fixed meal schedule and carbohydrate content 1

Initiating Insulin Therapy

When to Start Insulin

1. Immediate initiation indications:

   • Newly diagnosed with severe hyperglycemia causing ketosis or unintentional weight loss 1
   • Blood glucose ≥300-350 mg/dL (16.7-19.4 mmol/L) 1
   • HbA1c ≥10-12%, especially with symptoms 1
   • Acute illness, surgery, or pregnancy 2

2. Progressive initiation:

   • When oral medications fail to achieve glycemic targets 1
   • Consider when HbA1c ≥9% 1

Initial Regimen Selection

1. For most patients: Start with basal insulin + metformin ± one additional non-insulin agent 1
2. For severe hyperglycemia: Consider basal insulin plus mealtime insulin 1

Insulin Titration and Dose Adjustment

Basal Insulin Titration

• Adjust dose every 3 days based on fasting blood glucose patterns 3:
  • 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%

Prandial Insulin Titration

• Adjust each meal dose separately based on 2-hour postprandial glucose 3:
  • PPG >200 mg/dL: Increase by 2-4 units
  • PPG 150-200 mg/dL: Increase by 1-2 units
  • PPG <100 mg/dL: Decrease by 1-2 units

Advancing Therapy

• If basal insulin has been titrated to appropriate fasting glucose but HbA1c remains above target:
  1. Add GLP-1 receptor agonist, OR
  2. Add prandial insulin before largest meal, OR
  3. Switch to twice-daily premixed insulin 1

Monitoring and Self-Management

Blood Glucose Monitoring

• Check blood glucose at least 4 times daily (fasting, before meals, bedtime) 3
• Add occasional 2-hour postprandial checks to evaluate meal coverage
• Increase monitoring frequency when changing insulin regimens 4

Patient Education

• Provide comprehensive education on:
  • Self-monitoring of blood glucose
  • Hypoglycemia recognition and management
  • Consistent meal timing and carbohydrate content
  • Self-titration algorithms for insulin doses 1, 3

Special Considerations

Insulin Combinations with Other Medications

• Continue: Metformin with insulin therapy 1
• Consider continuing: SGLT2 inhibitors, thiazolidinediones (to improve glucose control and reduce total daily insulin dose) 1
• Usually discontinue: Sulfonylureas, DPP-4 inhibitors, and GLP-1 receptor agonists when using complex insulin regimens beyond basal insulin 1

Common Pitfalls to Avoid

1. Overbasalization: Signs include basal dose >0.5 units/kg, large bedtime-morning glucose differential, hypoglycemia 1
2. Delayed intensification: Insulin therapy should not be delayed in patients not achieving glycemic goals 1
3. Medication errors: Always check insulin labels before administration to avoid mix-ups 4
4. Lipohypertrophy: Rotate injection sites to prevent poor insulin absorption 4
5. Ketoacidosis with SGLT2 inhibitors: Monitor for symptoms if combining with insulin 1

Safety Precautions

• Never share insulin pens, syringes, or needles between patients 4
• Administer subcutaneously into the abdominal area, thigh, or deltoid 4
• Rotate injection sites within the same region 4
• Do not dilute or mix with any other insulin or solution 4

By following these guidelines for insulin therapy initiation and management, healthcare providers can help patients with diabetes achieve optimal glycemic control while minimizing risks of hypoglycemia and other complications.