Insulin To Carb Ratio Calculator

Variables and formula

This calculator provides the I:C ratio and the necessary number of insulin units and can help clinicians or patients customize their dosage.

Please note that this tool is for information purposes and only a medical specialist should decide your medication dosage.

■ The first tab determines the insulin to carb ratio based on the insulin units prescribed:

ICR (x from 1:x) = Carbohydrate intake in grams / Number of daily insulin units

■ The second tab helps determine the number of insulin units required after a specific carbohydrate intake, based on a known I:C ratio:

Carb coverage = Carbohydrate intake in grams / ICR (x from 1:x)

Insulin dosage guidelines

Insulin dosage that appropriately corrects high blood sugar levels needs to consider the carbohydrate content of meals and snacks.

The daily insulin dosage is divided in two approximately equal components:

■ A constant component: also known as basal insulin replacement, that is used to replace insulin overnight during fasting (between meals).

■ A customizable dose: modifiable based on carbohydrate coverage and used to correct abnormal blood sugar. This component is prescribed as insulin to carbohydrate ratio.

When prescribing insulin, there are several approaches:

*Factors that influence sensitivity to insulin vary on an individual basis, with level of physical activity and even time of day (some patients require a larger dosage in the morning). Sensitivity is quantified by how efficient the sugar correction is.

Rapid acting insulin aims to regulate the heightened levels and is more effective than insulin with slow action. One unit of insulin usually determines a decrease in blood sugar level of 50 mg/dL.

Commercial insulin products have varying I:C ratio, from 1:4 to 1:30, with most products having an I:C ratio of 1:12 or 1:15. This means that one unit disposes of 12 to 15 grams of carbohydrate.

Carbohydrate counting

Carb counting is an approach to dosing insulin that is commonly used by type 1 diabetes patients on the basal bolus insulin regimen as a method of blood glucose management, dependent on carb intake.

The method involves the monitoring of all dietary carbohydrates. These include sugars, starches and fiber, however, the former is not counted as blood sugar elevating factor.

Carbohydrate consumption is defined as grams or portions (1 portion = 10 g). In more advanced calculations, the glycemic index may also be calculated. Information about carbs can be found in:

■ Food labels;

■ Nutritional information;

■ Reference lists;

■ Online recipe information for restaurants.

The 500 rule

There is a less specific rule for daily carbohydrate intake that states that about 500 grams of daily diet is made up of carbs. This means that by dividing this to the number of prescribed insulin units, the I:C ratio can be extracted. (tab 1)

In the table below you can find the average insulin units in different dosage plans and their corresponding ratios based on the 500 grams approach:

References

1. Bergenstal RM, Johnson M, Powers MA, Wynne A, Vlajnic A, Hollander P, Rendell M. Adjust to target in type 2 diabetes: comparison of a simple algorithm with carbohydrate counting for adjustment of mealtime insulin glulisine. Diabetes Care. 2008; 31(7):1305-10.

2. Cresswell P, Krebs J, Gilmour J, Hanna A, Parry-Strong A. From 'pleasure to chemistry': the experience of carbohydrate counting with and without carbohydrate restriction for people with Type 1 diabetes. J Prim Health Care. 2015; 7(4):291-8.

3. Mendosa: Insulin-to-Carb Ratios Made Easy; Gary Scheiner, MS, CDE; 2015.