A Simple Insulin Dosage Calculator

By Neil Bason,

For people who inject insulin with a basal/bolus regimen, it’s often difficult to calculate the proper pre-meal dose. I have decided to design a simple electronic calculator to mimic the mental process used to calculate meal-time dose of insulin.

To calculate the number of meal-time insulin units to inject, you must establish the following:

1. Blood sugar level - (using a blood glucose meter). 2. Carb Ratio - input carb ratio e.g. 1.5 (Insulin resistance)3. The grams of carbohydrates consumed4. The amount of exercise to be taken post-injection.

Typically the mental process you undertake to calculate your insulin dose is as follows:

1. Blood Sugar: (mg/dl) Suppose your blood sugar reading is 195 and your target blood sugar is 105. Subtracting 105 from 192, = 87. One insulin unit lowers your blood sugar by approximately 55 points, so you divide 87 by 55 to get 1.58 which is the number of insulin units you need to normalize your current blood sugar.

2. Carb Ratio: when this is displayed, you should input your insulin ratio (as instructed by your diabetic educator) 0; 1.0; 1.5; 2.0; 2.5; 3.0; 3.5. (If you are not on a ratio regime then you simply input 1 and test your blood to adjust). This may be different at each mealtime. 3. Carbohydrates: When Carb/Grams is displayed count carbohydrate grams as instructed by your diabetic educator, then enter the number of Grams for example 60 grams. (This number is automatically divided by 10 and multiplyed by the carb ratio).

4. Exercise: If post-injection activity is planned, then you need to calculate how much less insulin will be necessary, this is taken as a percentage of the total insulin, so for example inputting 0 means that no post injection will be taken, inputting 3 (medium exercise like an afternoons shopping) will subtract 30% from the calculated total insulin dosage.

The above is the process that you carry out at every meal. The Insulin Unit Calculator merely mimics this process, as follows:

mg/dl versionWhen the calculator is turned on, Blood Sugar appears on the display input your blood sugar reading (192) and press the ENTER key. The calculator automatically makes your first calculation: 192 – 105 = 87 ÷ 55 = 1.58 units

As soon as the ENTER key is pressed, Ins/Carb ratio is displayed, input your insulin ratio say 1.5 (as instructed by your diabetic educator) then press ENTER key.

As soon as the ENTER key is pressed, Carbohydrates appears on the display. You now mentally calculate the grams of carbohydrates you consumed, for example, 60 carbs. The calculator automatically divides this number by 10 and then multiplies it by the carb ratio (1.5) so 60 grams is calculated: 60 ÷ 10 = 6 x 1.5 = 9 units.

Exercise then appears on the display to prompt you to think about upcoming exercise. The calculator offers six options, from zero to five. 0 denote no exercise, and 5 denote heavy exercise. If 2 is entered, the calculator subtracts 20% of the insulin from the equation.

When the ENTER key is pressed following the exercise input, the calculator automatically makes the total calculation: 192 – 105 = 87 ÷ 55 = 1.58 + (1.5 x 6 = 9) = 10.58 – 2 (20%) = 8.4 insulin units.

Insulin Dose Calculator

The above may look complicated, but using the calculator is really very simple, all you do is the following:

Enter your blood sugar reading (192) Enter carb ratio (1.5)Enter Carb/Grams (60)Enter an exercise value to compensate for exercise (2)The calculator then displays the insulin units to be injected (8.4 Insulin Units)

By Neil BasonThorpe Products Ltd.Cambridge UKneil@thorpe-products.comwww.thorpe-products.com