How to Calculate Your Insulin Sensitivity Factor


Healthcare professionals use the 1500 and 1800 Rules to calculate an insulin sensitivity factor.

  • The 1500 Rule estimates the point drop in mg/dL for every unit of Regular insulin taken.

  • The 1800 Rule estimates the point drop in mg/dL for every unit of rapid-acting insulin taken. 
     

The calculation is based on all of the units of insulin that a person takes in one day.
 
1. In the chart below, look up a total daily dose of insulin in the left column.
 
2. Slide your finger across to either the Rapid-acting Insulin column in the middle, or the Regular insulin column on the right. The number in the column is the estimated point drop in blood glucose per one unit of that insulin. That is the insulin sensitivity factor.
 

Example 1: A woman takes 15 units of Humalog and 25 units of NPH per day, for a total daily insulin dose of 40 units. Reading in the Humalog column, her insulin sensitivity factor is 45 mg/dL (1800 divided by 40). Her blood glucose will be lowered by approximately 45 mg/dL for every unit of Humalog she takes.

Example 2: A man takes 20 units of Regular and 25 units of NPH daily, for a total of 45 units per day. His insulin sensitivity factor is 33 mg/dL (1500 divided by 45).

Example 3: A young girl takes 20 units of Regular insulin and 15 units of Lantus daily, for a total daily insulin dose of 35 units. Her insulin sensitivity factor is 43 mg/dL (1500 divided by 35).


 Insulin Sensitivity Factors:
 

1800 Rule 1500 Rule
Total Daily
Insulin Dose

Point Drop per Unit of
Rapid-acting Insulin

Point Drop per Unit of
Regular Insulin
20 90 mg/dL 75 mg/dL
25 72 mg/dL 60 mg/dL
30 60 mg/dL 50 mg/dL
35 51 mg/dL 43 mg/dL
40 45 mg/dL 38 mg/dL
50 36 mg/dL 30 mg/dL
60 30 mg/dL 25 mg/dL
75 24 mg/dL 20 mg/dl
100 18 mg/dL 15 mg/dL


Adapted from Type 1 Diabetes - a Guide for Children, Adolescents, Young Adults and Their Caregivers; Ragnar Hanas MD, PhD; 2005 Marlowe & Company, NY

Important Note: The 1800/1500 Rule is mostly useful for people with type 1 diabetes. People with type 2 diabetes should check with their doctor.


Important Note: The content of this web site is not intended to be a substitute for professional medical advice, diagnosis or treatment. Do not disregard your doctor's advice or delay in seeking it because of something you have read on this web site.

NovoLog is a trademark of Novo-Nordisk, AIS
Humalog is a trademark of Eli Lilly and Company
Lantus is a trademark of Sanofi-Aventis Deutschland GmbH

 


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Important Note: The content of this website is not intended to be a substitute for professional medical advice, diagnosis or treatment. Do not disregard your doctor's advice or delay in seeking it because of something you have read in this website.

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