In Flexible insulin therapy (FIT), each mealtime insulin dose has two components:
That's what makes this type of insulin therapy flexible. It allows you to change the insulin dose to fit your lifestyle. Calculating a mealtime dose takes a little practice, but it is not that hard. In fact, some of the newer insulin pumps have a built-in calculator that does this for you. Let's look at the steps in detail.
Step 1: Cover the Carbohydrates
In order to cover the total carbohydrate servings in a meal you need to know your insulin-to-carb ratio. This ratio may be 1 to 15 (written as 1:15) for someone who is very sensitive to insulin. The ratio might only be 1:5 for someone who is less sensitive to insulin.
A ratio of 1:10 means that for every 10 grams of carbohydrate they eat, a person needs to inject 1 unit of rapid- or short-acting insulin. Your doctor can help you find the carb-to-insulin ratio that is right for you.
Step 2: Add or Subtract a Correction Dose of Insulin based on your Blood Glucose Level
To do this, you must know your Insulin Sensitivity Factor (ISF). This is sometimes called a ‘correction factor’. Your insulin sensitivity factor is simply a measure of the impact that insulin has on your particular body. Put a bit more technically, it’s the amount by which your blood glucose is reduced by one unit of rapid- or short-acting insulin in a period of two to four hours.
Your doctor can tell you what your insulin sensitivity factor is. For most people with diabetes, it is typically between 30 and 50 mg/dL.
To calculate a blood glucose correction dose: