CALCULATING YOUR INSULIN SENSITIVITY FACTOR (ISF)
Your Diabetes Team may use any of the following methods to help find your ISF:
1. Insulin/Blood Glucose Formula
(One unit of rapid or short-acting insulin for every 50 mg/dl increase or decrease in your blood glucose level).
2. Rule of 1500 – if you are using shortacting insulin (Regular).
3. Rule of 1700 – if you are using rapidacting insulin (Humalog®, Novalog®, Apidra®).
ISF Method I – Insulin/Blood
With ISF Method I, you take one unit of rapid or short-acting insulin for every 50 mg/dl increase or decrease in your blood glucose level.
Blood glucose target is 100 mg/dl.
John’s pre-lunch blood glucose is 180 mg/dl and his Insulin Sensitivity is 50.
His reading shows that he is above his target by 80 mg/dl.
[180 mg/dl – 100 mg/dl = 80 mg/dl]
He should take 1 (1.5 if you measure 1/2 units) extra units at lunch.
If his usual dose of rapid or short-acting insulin at lunch were 12 units, he would increase it by one and take 13 or 13.5 units.
Blood glucose target: 100 mg/dl
Susan’s pre-lunch blood glucose is 205 mg/dl.
Her reading shows that she is above her target by 105 mg/dl
[205 mg/dl – 100 mg/dl = 105 mg/dl]
Q – How many extra units should Susan take?
105 mg/dl / 50 = 2 units
A – She should take 2 extra units. In this
case she should take a total of 14 units.
CALCULATING YOUR CARB:INSULIN RATIO
A carb:insulin ratio is the amount of rapid or short acting insulin you need to match or “cover” the amount of carbohydrate you eat.
The Rule of 500:
Add up all the insulin given for 24 hours and divide it into 500. The answer is
your carb:insulin ratio.
Your total insulin dose is 50 units.
500 divided by 50 = 10
Your carb: insulin ratio is 10:1
Insulin needed for carbohydrates 9 units (90 carbohydrates divided by 10)
Insulin needed to correct for high blood glucose (190-100=90) divided by 30 (ISF)=3
Total insulin for food and carb 9 + 3 = 12 units
Reduction for high intensity exercise (Step 5) 3 unit
TOTAL amount of pre-dinner insulin 9 units