What is the typical starting dose and administration schedule for a 70/30 (seventy/thirty) combined insulin regimen in patients with type 2 diabetes mellitus?

Starting Dose and Administration Schedule for 70/30 Combined Insulin in Type 2 Diabetes

The typical starting dose for 70/30 combined insulin in type 2 diabetes is 0.1-0.2 units/kg/day administered twice daily, usually before breakfast and before dinner. 1

Initial Dosing Algorithm

1. Calculate starting dose:

   • For insulin-naive patients: 0.1-0.2 units/kg/day
   • Example: For a 70 kg patient, initial total daily dose would be 7-14 units/day

2. Administration schedule:

   • Divide total daily dose into two equal injections
   • Administer before breakfast and before dinner
   • NPH/Regular 70/30, aspart mix 70/30, or lispro mix 75/25 should be given:
     • 70/30 NPH/Regular: 30 minutes before meals
     • 70/30 aspart mix: 10 minutes before meals
     • 75/25 lispro mix: 10-15 minutes before meals

3. Dose titration:

   • Adjust dose every 3-4 days based on blood glucose patterns
   • Target fasting and premeal glucose: 80-130 mg/dL
   • Target 2-hour postprandial glucose: <180 mg/dL

Clinical Considerations

Advantages of 70/30 Insulin

• Provides both basal (70% intermediate-acting) and prandial (30% rapid/short-acting) coverage in a single injection
• Simplifies regimen for patients who need both basal and prandial insulin but prefer fewer injections
• More cost-effective than some insulin analogs 1

Limitations

• Less flexibility in meal timing compared to basal-bolus regimens
• May have suboptimal pharmacodynamic profiles compared to separate basal and bolus insulins 1
• Higher risk of hypoglycemia compared to basal insulin alone

Special Populations

• For elderly patients or those with renal impairment: Consider starting at lower doses (0.1 units/kg/day) to reduce hypoglycemia risk 1
• For patients with poor oral intake: Consider reducing dose or switching to a different regimen

Monitoring and Adjustment

• Monitor blood glucose levels regularly, especially before meals and at bedtime
• Evaluate HbA1c every 3 months to assess overall glycemic control
• If target HbA1c is not achieved with twice-daily dosing, consider:
  • Increasing to three-times daily premixed insulin (before each meal) 1
  • Switching to a basal-bolus regimen for better glycemic control

Common Pitfalls to Avoid

1. Inadequate dose titration: Failure to adjust insulin dose frequently enough (every 3-4 days) until targets are reached
2. Improper timing: Administering premixed insulin at incorrect times relative to meals
3. Missing complementary therapy: Continue metformin when starting insulin therapy unless contraindicated 2
4. Overlooking hypoglycemia risk: Educate patients on hypoglycemia recognition and management
5. Inappropriate use in type 1 diabetes: Premixed insulin alone is not appropriate for type 1 diabetes management

By following this structured approach to initiating 70/30 combined insulin therapy, patients with type 2 diabetes can achieve improved glycemic control with a relatively simple insulin regimen.