Calculating Insulin Sensitivity Factor (ISF)

Your insulin sensitivity factor (ISF) determines how much your blood sugar will drop in response to 1 unit of insulin. The total drop must be measured 2-3 hours later. It can vary, particularly in the morning, where you generally require more insulin to correct for a high blood sugar compared to the rest of the day.

Calculating your insulin sensitivity is quite easy. Just enter the amount of insulin, and the corresponding correction it gives you e.g. 3 units of insulin at breakfast time drops you 9 mmol/162mg.

Step 1. Enter Current Values

Meal time How much insulin? Gives you a BGL drop of...?   One unit of insulin covers:
Breakfast units  
Morning tea units (the same units are used below)  
Lunch units  
Afternoon tea units  
Dinner units  
Supper units  

Step 2. Review

Now you need to check if your ratios are right.

If you get low after a breakfast correction (test 2-3 hours after), then you are getting to much insulin and you need to increase the BGL drop given by 1 unit. Try adding 1mmol / 18mg, and then test with the new ratio. However, if you are getting too high after breakfast (test 2-3 hours after), then you need more insulin. Try reducing by 1mmol / 18mg, and then test with the new ratio.

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Available scenarios:

How does Low GI food affect my blood sugar?
Calculating Insulin Sensitivity Factor (ISF)
Calculating Carbohydrate Ratio
Should I inject before my meal?
Afreeza versus Humalog/Novolog/NovoRapid
Lucy thought she was Low
Undiagnosed versus diagnosed Type 2 diabetic

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