A Simple Insulin Dosage Calculator
By Neil Bason, Managing Director of Thorpe Products, Ltd. (a Type 1 Caregiver)
For people who inject insulin with a basal/bolus regimen, it's often difficult to calculate the proper pre-meal dose. After watching my partner struggle with the math for fifteen years, I decided to design a simple calculator to mimic the mental process that she uses to calculate her meal-time dose of insulin.
To calculate the number of meal-time insulin units to inject, you must establish the following:
- Blood sugar level (using a blood glucose meter).
- The grams of carbohydrates consumed, from which you derive the number of insulin units needed to cover that intake.
- The amount of exercise to be taken post-injection.
The mental process you must undertake to calculate your insulin dose is as follows:
1. Blood Sugar: Suppose your blood sugar reading is 195 and your target blood sugar is 100. Subtracting 100 from 195, you get 95, which is how much you need to lower your blood sugar. One insulin unit lowers your blood sugar by 55 points, so you divide 95 by 55 to get 1.7 is the number of units you need to lower your existing blood sugar.
2. Carbohydrates: Now you have to count carbohydrates to figure out how many additional units of insulin you need to inject to cover your carb intake. If your ratio of insulin to carbs is 1 unit to 10 grams, 60 grams of carbohydrates requires 6 additional units of insulin.
3. Exercise: If post-injection activity is planned, then you need to calculate how much less insulin will be necessary.
The above is the process that you carry out at every meal. The Insulin Unit Calculator merely mimics this process, as follows:
When the calculator is turned on, Blood Sugar appears on the display. You input your blood sugar reading (195) and press the ENTER key. The calculator automatically makes your first calculation: 195 - 100 = 95 ÷ 55 = 1.7.
As soon as the ENTER key is pressed, Carbohydrates appears on the display. You must now mentally calculate the grams of carbohydrates you consumed and then, based on your carb to insulin ratio, calculate the number of insulin units required to cover that carb intake. For example, 60 carbs at a 10:1 ration = 6 units of insulin. You key the number 6 into the calculator and press ENTER again.
Exercise then appears on the display to prompt you to think about upcoming exercise. The calculator offers four options, from zero to three. 0 denotes no exercise, and 3 denotes heavy exercise. If 2 is entered, the calculator subtracts 2 insulin units from the equation.
When the ENTER key is pressed following the exercise input, the calculator automatically makes the total calculation: 195 - 100 = 95 ÷ 55 = 1.7 + 6 = 7.7 - 2 = 5.7 units
The above may look complicated, but using the calculator is really very simple. All you do is the following:
Enter your blood sugar (195)
Enter insulin units to compensate for carbohydrates consumed (6)