Regular Insulin and NPH Insulin Combination Regimen
When combining regular (short-acting) insulin with NPH (intermediate-acting) insulin in adults with type 2 diabetes, initiate with a twice-daily split-mixed regimen: give 2/3 of the total daily dose before breakfast and 1/3 before dinner, with regular insulin drawn into the syringe first when mixing. 1
Initial Dosing Strategy
Starting NPH Insulin
- Begin with 10 units per day OR 0.1-0.2 units/kg per day when initiating basal NPH insulin alone 1
- Titrate by increasing 2 units every 3 days to reach fasting plasma glucose goal without hypoglycemia 1
- For hypoglycemia without clear cause, lower the dose by 10-20% 1
Adding Prandial Regular Insulin to NPH
When A1C remains above goal on bedtime NPH alone, you have two main approaches:
Option 1: Convert to Twice-Daily NPH Plan 1
- Calculate total dose as 80% of current bedtime NPH dose 1
- Distribute as 2/3 before breakfast, 1/3 before dinner 1
- Add 4 units of regular insulin to each injection OR 10% of the reduced NPH dose 1
Option 2: Add Prandial Insulin to Bedtime NPH 1
- Start with 4 units per day OR 10% of basal insulin dose with the largest meal 1
- Regular insulin can be dosed individually or mixed with NPH as appropriate 1
- Increase dose by 1-2 units or 10-15% based on postprandial glucose 1
Mixing Technique
Critical mixing order to prevent dosing errors:
- Always draw regular (short-acting) insulin into the syringe FIRST, then NPH 2
- This prevents contamination of the regular insulin vial with NPH 2
- Use only U-100 insulin syringes to avoid dosage errors 2
- The mixture should be injected within 15 minutes before a meal when rapid control is needed 1
Titration and Monitoring
Dose Adjustments
- Increase by 1-2 units or 10-15% of insulin dose based on glucose patterns 1
- Titrate each component (NPH and regular) separately based on individualized needs 1
- If A1C <8% (<64 mmol/mol), consider lowering basal dose by 4 units per day or 10% 1
Hypoglycemia Management
- Reduce corresponding dose by 10-20% if hypoglycemia occurs without clear cause 1
- Consider switching from evening NPH to a basal analog if recurrent hypoglycemia develops 1
Timing and Administration
Injection Timing
- Regular insulin should be given approximately 30 minutes before meals 2
- NPH in twice-daily regimens: morning dose before breakfast, evening dose before dinner 1
- Rotate injection sites within the same region (abdominal wall provides fastest absorption) 2
Storage Considerations
- Refrigerate unopened vials at 2-8°C (36-46°F) 2
- In-use vials can be kept unrefrigerated below 30°C (86°F) for up to 31 days 2
- Never use if insulin has become viscous, cloudy (for regular), or has changed color 2
Progression to Full Basal-Bolus
If A1C remains above goal on twice-daily mixed insulin:
Proceed to full basal-bolus plan 1
- Continue NPH as basal component (80% of previous NPH dose) 1
- Add regular insulin with each meal (4 units or 10% of reduced NPH dose per injection) 1
- Titrate each component independently based on fasting and postprandial glucose patterns 1
Important Caveats
When to Avoid This Regimen
- Do not mix insulin glargine with any other insulin due to low pH of its diluent 1
- Consider switching to basal analogs if patient frequently forgets evening NPH doses 1
- Avoid mixing phosphate-buffered insulins (NPH) with lente insulins 1
Special Considerations
- Premixed 70/30 formulations (70% NPH, 30% regular) can substitute for self-mixed regimens when the ratio matches patient needs 1
- This reduces injection burden and mixing errors 1
- Weight gain is more pronounced with daytime regular insulin (mean 3.4 kg) compared to bedtime NPH alone (1.9 kg) 3
- Consider GLP-1 receptor agonists in combination if cardiovascular disease is present or to mitigate weight gain 1