When should a 70/30 premixed insulin (70 % NPH, 30 % regular) be preferred over basal insulin glargine in an adult with type 2 diabetes requiring both basal and post‑prandial coverage on a simple twice‑daily regimen?

When to Use 70/30 Premixed Insulin Instead of Glargine

Use 70/30 premixed insulin (NPH/regular) when basal insulin alone has failed to achieve HbA1c targets despite adequate fasting glucose control, and the patient requires a simple twice-daily regimen with consistent meal timing and carbohydrate intake, particularly when cost is a significant barrier. 1, 2

Primary Indication: Basal Insulin Failure

• When basal insulin (glargine) has been titrated to achieve acceptable fasting glucose levels (80-130 mg/dL) OR the dose exceeds 0.5 units/kg/day, yet HbA1c remains above target, treatment intensification is required 1
• At this critical threshold, you have three equivalent options: (1) add rapid-acting insulin at the largest meal, (2) add a GLP-1 receptor agonist, or (3) switch to premixed insulin twice daily 2
• Studies demonstrate noninferiority between twice-daily premixed insulin and basal insulin plus single rapid-acting injection, with similar hypoglycemia rates 2

Clinical Scenarios Favoring 70/30 Over Glargine

Simplicity and Adherence

• Premixed 70/30 provides both basal and prandial coverage with only 2 injections daily (before breakfast and dinner), compared to 3-4 injections required for basal-bolus regimens 2, 3, 4
• This simplicity may improve adherence in patients who find multiple daily injections burdensome or have difficulty managing complex regimens 2, 4

Cost Considerations

• Human insulin 70/30 (Humulin 70/30, Novolin 70/30) is typically the most cost-effective insulin option, substantially less expensive than long-acting analogs like glargine 2, 5
• When cost is a significant barrier to care, 70/30 represents a practical alternative that can still achieve glycemic targets 2

Patient Characteristics

• Patients with consistent meal timing and carbohydrate intake are ideal candidates, as premixed insulin requires predictable eating patterns 2
• Those who prefer fewer daily injections over the flexibility of basal-bolus therapy 2

Critical Limitations: When NOT to Use 70/30

• Avoid in hospitalized patients: Randomized trials show premixed insulin causes significantly higher hypoglycemia rates (64% vs 24%) compared to basal-bolus regimens in the hospital setting, with no improvement in glycemic control 6, 1
• Irregular meal timing or variable carbohydrate intake: The fixed ratio of basal and prandial components cannot accommodate schedule variations 2
• Need for maximum flexibility: Basal-bolus regimens offer superior individualization for patients with unpredictable schedules 1

Dosing Algorithm for 70/30 Initiation

Starting Dose

• Begin with the total daily dose of current basal insulin 5
• Distribute as 2/3 before breakfast and 1/3 before dinner (not equal doses) 2, 5
• Example: If on glargine 50 units daily, start 70/30 at approximately 33 units morning and 17 units evening 5

Titration Protocol

• Increase by 2-4 units every 3 days based on fasting and pre-dinner glucose readings 5
• Target fasting glucose 80-130 mg/dL 1
• More frequent blood glucose monitoring is essential during transition, checking both fasting AND postprandial levels 2, 5

Pharmacodynamic Considerations

• The 70% NPH component provides intermediate-acting basal coverage over 12-16 hours 3, 7
• The 30% regular insulin component addresses postprandial glucose excursions, though with less optimal timing than rapid-acting analogs 2, 7
• Analogue premixes (70/30 aspart or 75/25 lispro) provide superior postprandial control compared to human insulin 70/30, though long-term HbA1c control is comparable 2, 3, 7

Medication Management During Transition

• Continue metformin when starting premixed insulin 2
• Discontinue sulfonylureas, DPP-4 inhibitors, and GLP-1 agonists when using premixed insulin regimens to avoid unnecessary complexity and hypoglycemia risk 2

Common Pitfalls to Avoid

Dosing Errors

• Never use the same dose morning and evening—the morning dose should be approximately twice the evening dose (2/3 vs 1/3 distribution) 2, 5
• Do not convert from basal insulin on a 1:1 basis without adjusting the distribution between injections 5

Patient Education Gaps

• Emphasize critical importance of consistent meal timing to prevent hypoglycemia, as the prandial component will peak regardless of food intake 2, 5
• Ensure adequate monitoring during the transition period when hypoglycemia risk is highest 2, 5

Inappropriate Use

• Do not use premixed insulin in type 1 diabetes—basal-bolus therapy has proved superior 8
• Avoid in critically ill or hospitalized patients due to unacceptably high hypoglycemia rates 6, 1

Alternative: When to Choose Glargine Instead

• Glargine remains the preferred initial insulin for most patients starting insulin therapy, beginning at 10 units daily or 0.1-0.2 units/kg/day 1
• Glargine offers once-daily dosing with predictable basal coverage and can be combined with metformin and other oral agents 1
• When flexibility in meal timing is important, basal-bolus therapy (glargine plus rapid-acting insulin) provides superior individualization compared to premixed formulations 1
• If cost is not a barrier and the patient can manage multiple injections, basal-bolus therapy generally offers better glycemic control with less hypoglycemia than premixed insulin 1, 6