Calculating Total Daily Insulin Dose When Switching from Humalog to 70/30 Insulin
When switching from Humalog (rapid-acting insulin lispro) to a 70/30 premixed insulin, start with the same total daily insulin dose divided into two equal injections given before breakfast and dinner, administered 30 minutes before meals. 1
Initial Dose Calculation
- Calculate your current total daily dose (TDD) of Humalog by adding all rapid-acting insulin doses given throughout the day 2
- Use this same TDD for the 70/30 insulin, splitting it equally: give 50% before breakfast and 50% before dinner 1, 3
- For example, if you're taking 40 units total of Humalog daily, start with 20 units of 70/30 before breakfast and 20 units before dinner 1
Important Dosing Adjustments
If you are currently taking more than 0.6 units/kg/day of insulin at home, reduce the total daily dose by 20% when switching to prevent hypoglycemia. 2 This is particularly important because:
- Premixed 70/30 insulin carries a 4-6 times higher risk of hypoglycemia compared to other insulin regimens 3
- The fixed ratio of 70/30 (70% intermediate-acting, 30% rapid-acting) provides both basal and prandial coverage simultaneously, which can lead to insulin stacking if dosed too aggressively 1
Titration Strategy After Initiation
- Adjust doses every 2 weeks based on fasting blood glucose, targeting 90-150 mg/dL 1
- If ≥50% of fasting values exceed goal: increase dose by 2 units 1
- If >2 fasting values per week are <80 mg/dL: decrease dose by 2 units 1
Critical Safety Warnings
Premixed 70/30 insulin has been associated with unacceptably high rates of hypoglycemia in hospital settings and is not recommended for inpatient use. 2 In outpatient settings:
- Patients must eat similar amounts of carbohydrates at consistent meal times to match the fixed insulin doses 3
- Carry quick-acting carbohydrates at all times due to elevated hypoglycemia risk 3
- Use lower starting doses (closer to 0.1 units/kg/day) for patients at high risk: age >65 years, renal failure, or poor oral intake 1
When This Switch May Not Be Appropriate
Do not use 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 Consider maintaining a basal-bolus regimen (separate basal and rapid-acting insulins) instead for these patients. 2, 3
Common Pitfall to Avoid
Do not continue escalating 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 to a basal-bolus regimen rather than continuing to increase premixed insulin, as this increases hypoglycemia risk without proportional glycemic benefit. 1