What dose of 70/30 insulin would a patient who takes Humalog (insulin lispro) 8 units TID and Lantus (insulin glargine) 28 units at bedtime need?

Converting from Basal-Bolus to 70/30 Insulin Regimen

For a patient taking Humalog 8 units TID (24 units total) and Lantus 28 units at bedtime (total daily dose = 52 units), start with 70/30 insulin at approximately 21 units before breakfast and 21 units before dinner (total 42 units/day), which represents an 80% conversion of the current total daily dose to account for the higher hypoglycemia risk with premixed insulin. 1

Step-by-Step Dose Calculation

Calculate Current Total Daily Dose

• Current regimen: Humalog 8 units × 3 meals = 24 units + Lantus 28 units = 52 units total daily dose 1

Apply the 20% Dose Reduction Rule

• The Endocrine Society recommends reducing the total daily dose by 20% when switching to 70/30 insulin if the patient is currently taking more than 0.6 units/kg/day to prevent hypoglycemia 1
• Reduced dose: 52 units × 0.80 = 41.6 units/day (round to 42 units) 1
• Split equally: 21 units before breakfast and 21 units before dinner 1

Why the 20% Reduction is Critical

• Premixed 70/30 insulin carries a 4-6 times higher risk of hypoglycemia compared to basal-bolus regimens 1
• The fixed 70:30 ratio provides both basal and prandial coverage simultaneously, which can lead to insulin stacking if dosed too aggressively 1

Titration Strategy After Initiation

Adjustment Schedule

• Adjust doses every 2 weeks based on fasting blood glucose, targeting 90-150 mg/dL 1
• If ≥50% of fasting values exceed goal: increase the dose by 2 units 1
• If >2 fasting values per week are <80 mg/dL: decrease the dose by 2 units 1

Monitoring Requirements

• Daily fasting blood glucose monitoring is essential during titration 2
• Patients must carry quick-acting carbohydrates at all times due to elevated hypoglycemia risk 1

Critical Safety Warnings

Patient Selection Considerations

• The European Association for the Study of Diabetes recommends against using 70/30 insulin in patients with unpredictable eating patterns or those requiring flexible dosing, as the fixed 70:30 ratio limits adjustment of basal versus prandial components separately 1
• The Lancet Diabetes and Endocrinology warns that premixed 70/30 insulin has been associated with unacceptably high rates of hypoglycemia in hospital settings and is not recommended for inpatient use 1

Dietary Requirements

• Patients must eat similar amounts of carbohydrates at consistent meal times to match the fixed insulin doses 1
• Administer 70/30 insulin 30 minutes before breakfast and dinner 3

Special Populations Requiring Lower Doses

• The American Geriatrics Society recommends using lower starting doses (closer to 0.1 units/kg/day) for patients at high risk, such as those aged >65 years, with renal failure, or with poor oral intake 1

When This Conversion May Not Be Appropriate

Consider Maintaining Basal-Bolus Instead

• The fixed 70:30 ratio limits adjustment of basal versus prandial components separately 1
• If the patient has unpredictable eating patterns, variable meal sizes, or requires flexible insulin dosing, maintaining the current basal-bolus regimen is preferable 1

Alternative: Consider Adding GLP-1 RA

• If A1C is above goal and the patient is not already on a GLP-1 RA, consider adding this class in combination with insulin rather than switching to premixed insulin 4

Common Pitfall to Avoid

• The American College of Endocrinology warns against continuing to escalate 70/30 doses indefinitely if A1C remains above target 1
• When basal insulin exceeds 0.5 units/kg/day, consider adding a GLP-1 receptor agonist or converting back to a basal-bolus regimen rather than continuing to increase premixed insulin 1
• Continue metformin unless contraindicated when making this insulin transition 2