ISF = 100/TDD (rapid-acting insulin) ISF = 83/ TDD (short-acting insulin)

The ISF formula provides an estimated starting point only. It will need to be individualized and modified based on SBGM results.

EXAMPLE (from DCPNS Insulin Dose Adjustment Policies & Guidelines Manual; 2002):

Sarah is a 15-year old teen with type 1 diabetes. She takes the following:

Before Breakfast NPH 15 u
Rapid-acting 6u
Before Supper Rapid-acting 5u
Bedtime NPH 8u
TDD 34u

Her target blood glucose range is 4 to 7 mmol/L ac meals.

Sarah's TDD is 34 u, and she uses rapid-acting insulin.
Sarah's ISF is: 100/34= 2.9 mmol/L (3 mmol/L)

That is, 1 u of rapid-acting insulin will lower her blood glucose by 3 mmol/L.

If Sarah was using short-acting insulin, her ISF would be: 83/34 = 2.4 mmol/L (2 mmol/L)

That is, 1 u of short-acting insulin would lower her blood glucose by 2 mmol/L.


1. Husband A, Trussell R. Kids are pumping: the Alberta Children's Hospital experience. Canadian Diabetes. 2000;13(2):3-6.