How do I switch from NPH (Neutral Protamine Hagedorn) Humulin N (insulin isophane) to 70/30 insulin?

Switching from NPH Insulin to 70/30 Insulin

When switching from NPH (Humulin N) insulin to 70/30 insulin, stop the NPH insulin and start twice-daily 70/30 insulin with the total daily dose equal to 80% of the previous NPH dose, typically dividing as 2/3 before breakfast and 1/3 before dinner. 1

Conversion Process

Initial Dosing

• Calculate the total daily dose of 70/30 insulin as 80% of your current NPH insulin total daily dose 1
• Divide the 70/30 insulin into two daily injections 1:
  • Give 2/3 of the total daily dose before breakfast
  • Give 1/3 of the total daily dose before dinner
• For example, if you were taking 50 units of NPH daily, your new 70/30 insulin regimen would be approximately 40 units total (80% of 50), with 27 units before breakfast and 13 units before dinner 1

Timing of Administration

• Administer 70/30 insulin before meals (typically 30 minutes before for human insulin mix) 2
• 70/30 insulin contains 70% NPH (intermediate-acting) and 30% Regular (short-acting) insulin components 2

Monitoring and Adjustment

Blood Glucose Monitoring

• Check blood glucose levels more frequently during the transition period 1
• Monitor both fasting and postprandial glucose levels to assess the effectiveness of the new regimen 1
• Target fasting glucose values between 4.0-7.0 mmol/L (72-126 mg/dL) 1

Dose Titration

• Adjust the morning and evening doses separately based on blood glucose patterns 1
• For hypoglycemia: determine the cause and if no clear reason is found, lower the corresponding dose by 10-20% 1
• For persistent hyperglycemia: increase the dose by 1-2 units or 10-15% at a time 1

Clinical Considerations

Advantages of 70/30 Insulin

• Provides both basal and prandial coverage with fewer daily injections 1
• Simplifies the regimen compared to separate basal and bolus injections 1
• May improve adherence due to convenience of premixed formulation 3
• Studies show patients with poor control on self-mixed insulin regimens can safely transfer to premixed 70/30 insulin, often with improved glycemic control 3

Potential Challenges

• Less flexibility in dosing compared to basal-bolus regimens 1
• May not provide optimal coverage for variable meal timing or content 1
• The fixed ratio may not match individual physiologic needs as precisely as separately adjusted basal and bolus components 1

Special Considerations

Hypoglycemia Risk

• Monitor closely for hypoglycemia during the transition period, especially at night 1
• Premixed insulin regimens may have different hypoglycemia risk profiles compared to NPH alone 4
• Consider reducing the dose if A1C is <8% when switching to avoid hypoglycemia 1

Meal Timing

• More consistent meal timing is important with premixed insulin regimens 1
• The 30% regular insulin component addresses postprandial glucose excursions 2
• The 70% NPH component provides intermediate-duration basal coverage 2

Common Pitfalls to Avoid

• Don't convert on a 1:1 basis: Using 80% of the NPH dose when converting to 70/30 insulin helps prevent hypoglycemia 1
• Don't use the same dose for both morning and evening: The 2/3 morning and 1/3 evening split better matches physiologic needs 1
• Don't neglect monitoring during transition: More frequent glucose monitoring is essential during the switch 1
• Don't forget about meal timing: 70/30 insulin should be administered approximately 30 minutes before meals for optimal effect 2