When should a 70/30 premixed insulin (70% NPH protamine suspension and 30% regular insulin) be used in an adult with type 2 diabetes?

When to Use 70/30 Insulin in Type 2 Diabetes

Use 70/30 premixed insulin (NPH/regular) when basal insulin has been titrated to achieve fasting glucose of 80-130 mg/dL or the dose exceeds 0.5 U/kg/day, yet HbA1c remains above target, particularly when the patient needs a simple twice-daily regimen with consistent meal timing and cost is a major concern. 1

Primary Clinical Indication

Treatment intensification after basal insulin failure is the key scenario for initiating 70/30 insulin. 1 When basal insulin alone (such as glargine) fails to achieve HbA1c targets despite adequate fasting glucose control, you have three equivalent options:

• Premixed insulin twice daily (before breakfast and dinner) 1
• Adding rapid-acting insulin at the largest meal 1
• Adding a GLP-1 receptor agonist 1

Studies demonstrate noninferiority between twice-daily premixed insulin and basal insulin plus single rapid-acting injection, with similar hypoglycemia rates. 1

Specific Patient Populations Who Benefit Most

Cost-Conscious Patients

• Human insulin 70/30 formulations (Humulin 70/30, Novolin 70/30) are the most cost-effective insulin options available 1, 2
• This is particularly important when cost is a significant barrier to therapy 1

Patients Preferring Fewer Injections

• Premixed formulations provide both basal and prandial coverage with only 2 injections daily, compared to 3-4 injections required for basal-bolus regimens 1
• This may improve adherence in patients who find multiple daily injections burdensome 1

Patients with Consistent Routines

• Choose premixed insulin if the patient has consistent meal timing and carbohydrate intake 1
• The fixed ratio requires predictable eating patterns to prevent hypoglycemia 1, 2

Algorithmic Approach to Initiation

Step 1: Confirm Basal Insulin Inadequacy

• Fasting glucose at target (80-130 mg/dL) OR basal insulin dose >0.5 U/kg/day 1
• HbA1c remains above target despite adequate basal dosing 1

Step 2: Assess Patient Suitability

• Patient prefers fewer daily injections over basal-bolus regimen 1
• Patient has consistent meal timing and carbohydrate intake 1
• Cost is a significant barrier (consider human insulin 70/30) 1

Step 3: Initiate Dosing

• Distribute total daily dose as 2/3 before breakfast and 1/3 before dinner 2
• Never use the same dose for morning and evening injections 2
• Do not convert from basal insulin on a 1:1 basis without adjusting distribution 1, 2

Critical Contraindications

Absolute Contraindications

Avoid premixed insulin in hospitalized or critically ill patients - randomized trials show premixed insulin leads to markedly higher hypoglycemia rates (approximately 64% vs 24% with basal-bolus regimens) without improving overall glycemic control. 1

Relative Contraindications

• Irregular meal timing or variable carbohydrate intake 1
• Maximum flexibility in meal planning is required 1
• Unpredictable meal times necessitate basal-bolus therapy for superior individualization 1

Advantages Over Alternative Regimens

Compared to Basal-Bolus

• Fewer daily injections (2 vs 4+) with noninferior glycemic control 1
• Simpler regimen that may improve adherence 2

Compared to Basal + GLP-1 Agonist

• Less expensive 1
• May be better tolerated (GLP-1 agonists associated with GI side effects) 1

Compared to Human Insulin 70/30

• Analogue premixes (such as insulin aspart 70/30) provide superior postprandial glucose control 1
• Long-term HbA1c control is comparable between formulations 1
• Human insulin 70/30 remains appropriate for patients with cost concerns, relaxed A1C goals, or prominent insulin resistance 1

Essential Monitoring Requirements

During Transition Period

• More frequent blood glucose monitoring is essential 2, 3
• Monitor both fasting AND postprandial glucose levels 1, 2
• This is when hypoglycemia risk is highest 1, 2

Ongoing Targets

• Target fasting glucose 80-130 mg/dL 1
• Use fasting glucose values to guide dose titration 1

Medication Management During Initiation

Continue

• Metformin when starting premixed insulin 1

Discontinue

• Sulfonylureas 1
• DPP-4 inhibitors 1
• GLP-1 agonists when using multiple-dose premixed insulin regimens 1

Common Pitfalls to Avoid

Dosing Errors

• Never use same dose for morning and evening - morning dose should be higher (2/3 vs 1/3 distribution) 1, 2
• Do not convert from basal insulin on 1:1 basis without adjusting distribution 1, 2

Patient Education Gaps

• Emphasize critical importance of consistent meal timing to prevent hypoglycemia 1, 2
• Ensure adequate monitoring during transition period when hypoglycemia risk is highest 1, 2
• Meal timing becomes more critical with premixed insulins compared to basal-bolus regimens 2, 3

Monitoring Failures

• Never neglect monitoring during the transition period 2, 3
• Don't focus solely on fasting glucose - postprandial values are equally important 1, 2