What is the recommended starting dose of insulin 70/30 (Novolin 70/30, NPH insulin (Novolin N) and regular insulin) for a patient with type 2 diabetes mellitus?

Insulin 70/30 Starting Dose for Type 2 Diabetes

Start insulin 70/30 at 12 units before dinner (or 0.2 units/kg/day split as two-thirds before breakfast and one-third before dinner if initiating twice-daily dosing), administered in combination with metformin. 1

Initial Dosing Strategy

Once-Daily Initiation (Preferred Starting Approach)

• Begin with 12 units of insulin 70/30 administered 30 minutes before dinner 2
• This simplified approach allows patients to transition safely from oral agents to insulin therapy 2
• Continue metformin throughout the transition 1
• Discontinue sulfonylureas to prevent hypoglycemia 1

Twice-Daily Initiation (Alternative Approach)

• Total starting dose: 0.2 units/kg/day 3
• Split as 55:45 to 60:40 ratio (morning:evening) - this means approximately 11-12 units before breakfast and 8-9 units before dinner for a 70 kg patient 3
• The higher morning dose ratio (55-60% of total daily dose) is more appropriate than a 50:50 split, as studies show patients starting at 50:50 require upward adjustment of the morning dose 3
• Administer 30 minutes before breakfast and 30 minutes before dinner 1

Titration Protocol

Target Fasting Blood Glucose

• Increase dose by 2 units every 3 days until fasting plasma glucose reaches 80-110 mg/dL 4
• For once-daily evening dosing, titrate based on pre-breakfast fasting blood glucose 4
• For twice-daily dosing, adjust morning dose based on pre-dinner glucose and evening dose based on fasting morning glucose 3

Hypoglycemia Management

• If hypoglycemia occurs without clear cause, reduce the corresponding dose by 10-20% 1, 5
• Monitor closely during initial titration phase 5

Intensification Strategy When HbA1c Remains Above Target

Adding Second Daily Injection (if starting once-daily)

• At 16 weeks, if HbA1c >6.5%, add 6 units of insulin 70/30 before breakfast 4
• Titrate the morning dose to achieve pre-dinner blood glucose of 80-110 mg/dL 4
• This approach achieves glycemic targets (HbA1c <7%) in 70% of patients 4

Adding Third Daily Injection

• If HbA1c remains >6.5% after 32 weeks on twice-daily dosing, add 3 units before lunch 4
• Titrate based on 2-hour post-lunch glucose to achieve 100-140 mg/dL 4
• Three times daily dosing achieves HbA1c <7% in 77% of patients 4

Important Clinical Considerations

Medication Adjustments

• Metformin must be continued - this combination is the foundation of the regimen 1, 2
• Discontinue sulfonylureas to prevent additive hypoglycemia risk 1
• Discontinue DPP-4 inhibitors when using intensive insulin regimens 1

Cost Considerations

• Insulin 70/30 NPH/regular is significantly less expensive than rapid-acting insulin analogues (70/30 aspart, 75/25 lispro) 1
• Human regular insulin and 70/30 NPH/regular products can be purchased for considerably less than average wholesale prices at select pharmacies 1
• The pharmacodynamic profile of NPH/regular 70/30 may be suboptimal compared to analogue premixes, but cost savings are substantial 1

Common Pitfalls to Avoid

Timing Errors

• NPH/regular 70/30 requires 30-minute pre-meal administration (unlike rapid-acting analogues which can be given 10-15 minutes before meals) 1, 2
• Failure to allow adequate time before eating reduces postprandial glucose control 2

Inadequate Titration

• Therapeutic inertia is common - providers must actively titrate every 3 days based on glucose monitoring 4
• Patients achieving fasting glucose <126 mg/dL experience the largest HbA1c reductions (-1.8% to -2.3%) 2

Overbasalization Signals

• If basal dose exceeds 0.5 units/kg/day, consider switching regimens rather than continuing to increase premixed insulin 1
• Elevated bedtime-to-morning glucose differential suggests need for different insulin strategy 1
• High glucose variability or recurrent hypoglycemia indicates the fixed-ratio premix may not be appropriate 1

Conversion Errors

• When converting from 70/30 to NPH alone, use only 80% of the total daily dose to prevent hypoglycemia 5
• The 70/30 formulation contains both basal (70% NPH) and prandial (30% regular) components, so direct 1:1 conversion to basal-only insulin causes inadequate coverage 5