How much do I give? Reevaluation of insulin dosing estimation formulas using continuous glucose monitoring

To reevaluate current formulas for determining the total basal insulin dosage (TBD), insulin to carbohydrate ratio (ICR), and correction factor (CF) from weight or total daily dosage (TDD) in pump-treated patients with type 1 diabetes mellitus.

From a post hoc analysis of data from 4 previously published studies, subjects who met the inclusion criteria were selected. No subject was duplicated. For all studies, the basal glucose target was to have fewer than 20%of glucose readings greater than 170 mg/dL and to have 10% or fewer glucose readings less than 70 mg/dL. Bolus insulin was adjusted to achieve a 2- to 4-hour postbolus glucose value within 20% of the premeal glucose (ICR) or 80 to 120 mg/dL from premeal hyperglycemia (CF). In the first 2 studies, dosing titration by CGM was performed from 72-hour CGM tracings every week to every 6 weeks. In the other 2 studies, 24- to 72-hour CGM downloads and insulin adjustments were done each weekday.

Of 101 participants, 61 (59% women) met the inclusion criteria. Estimation formulas could be rounded to the following: TBD = 0.2 x weight (kg) or 0.4 x TDD; ICR = 300 / TDD; and CF = 1500 / TDD. In particular the relationship between all 3 dosing factors could be represented as 100 / TBD = ICR = CF / 4.5.

These results suggest that current formulas give a higher estimate for TBD and a lower estimate for the bolus dose.