Meal related insulin boluses are calculated according to
the carbohydrate content of the meal using the carbohydrate-to-insulin
ratio (CIR)
The carbohydrate-to-insulin ratio (CIR) is the number of grams of
carbohydrate that are covered by 1 unit of insulin. The CIR is calculated
by dividing the constant 450 by the Total Daily Dose (TDD).
The CIR may be different for different meals of the day.
CIR-= 450 / TDD
Example:
TDD= 50 units insulin
CIR= 450 /50 = 9 grams/unit
The meal has 90 grams of carbohydrate
Meal insulin bolus = carbohydrates/carbohydrate to insulin ratio CIR =90/9= 10 units
- If the post meal blood sugar is above the targeted blood
sugar range for 2 to 3 days then consider decreasing the CIR by 10 to 20
percent
- If the post meal blood sugar is less than the targeted
blood sugar range for 2 to 3 days then consider increasing the CIR by 10 to 20
percent
Calculation of Correction Dose
If the premeal blood sugar is out of the targeted range , the
meal related insulin dose may need to be adjusted accordingly. To return
the blood sugar to the desired premeal blood sugar from the current blood
sugar it is necessary to determine the amount blood glucose is lowered by
the injection of 1 unit of insulin. The amount blood glucose is lowered by the injection of 1 unit of insulin
is called the insulin sensitivity factor (also known as the correction
factor) , and is calculated by dividing
the constant 1700 by the Total Daily Dose (TDD) of rapid acting insulin
or dividing the constant 1500 by the Total Daily Dose of insulin (TDD) of
short acting insulin.
Insulin Sensitivity Factor (Correction Factor) =
1700 / TDD
Example
TDD= 50 units insulin
ISF= 1700 /50 = 34 mg/dL
The current premeal blood sugar is 160 mg/dL
The target premeal blood sugar is 90 mg/dL
Correction dose =
(Current blood sugar -Target blood sugar) / ISF = (160-90)/ 34
= 2.1 units
