Chapter 13 - Carbohydrate Counting and Precise Insulin Dosing

Abstract

Precise mealtime insulin dosing requires accurate carbohydrate counting and an appropriate carbohydrate-to-insulin ratio (C:I ratio) that produces a premeal to 2-hour postmeal blood glucose (BG) excursion of 30 to 50mg/dL. The C:I ratio is an estimate of the grams of carbohydrate that each 1 unit of insulin will cover; a C:I ratio of X:1 means that 1 unit of insulin should be given for each X grams of carbohydrate to be consumed. The initial C:I ratio for each person is often calculated as follows: 500/Total daily dose (TDD) of insulin. A correction factor (CF) is the amount of insulin that should be added to the mealtime dose when the premeal BG is above the target range or that is taken between meals to correct high BG values. The CF is an estimate of the expected BG drop for each 1 unit of insulin given when the BG is elevated above the goal; a CF of N:1 means that a person should take 1 unit of insulin for every N mg/dL the current BG level is above the individualized target. We calculate an initial CF for each person as 1650/TDD. The effectiveness of the C:I ratio and the CF should subsequently be evaluated at each visit. Accurate carbohydrate counting and insulin dose calculation are crucial skills for all people who use intensive insulin therapy with multiple daily insulin injections or with insulin pumps. Providers should also have basic skills in carbohydrate counting and insulin dose calculation. This chapter presents 10 practice cases for the reader to practice carbohydrate counting and insulin dosing calculations.