• Stories
  • Useful Links

It is important to remember that even when you are adjusting your insulin dose for what you eat, there will still be times when your blood glucose levels will run higher than it should.  During these times you should correct your blood glucose to your individual target as agreed with your diabetes team.

There are guidelines for the correction of blood glucose levels known as the 100 Rule.  By dividing the amount of insulin you take each day into 100 you will get an estimate of how much 1 unit of rapid acting insulin will affect your blood glucose levels. 

For example:

If you take 50 units of insulin per 24 hours, 100/50 = 2

Therefore every 1 unit of rapid acting insulin will reduce your blood glucose levels by 2 mmol/l.

The 100 Rule is also known as your ‘Insulin Sensitivity Factor’.  Your diabetes team can work this out for you.  Remember that you might need different targets at different times of the day or different sensitivity rates at different times of the day.

Points to Remember:

  • Be aware of ‘insulin stacking’.  Remember that 50% of rapid acting insulin is still active for 2 hours after it was administered.
  • The effects of insulin on your blood glucose can differ depending on, for example, the amount of insulin you have taken, exercise, site administered to, sickness.
  • This method of correction should not be used when you are ill.  Instead you should refer to guidance or sick day rules that your diabetes team provided you with.

Calculating a Correction Dose

To calculate a correction dose, follow the equation below:

Actual BG level  –  Target BG level = Correction Dose
Correction Factor or Insulin Sensitivity Factor

For example:

14mmol/l  - 8mmol/l  = 3 units of rapid acting insulin

Contact your diabetes team for advice if you are unsure.

Points to remember:

  • Try to keep correction doses to less than 10% of your total daily dose
  • Speak to your diabetes team if you are unsure or are correcting frequently as your insulin doses may need to be adjusted
  • Use caution with correction doses after exercise (you may need less insulin than calculated)

Need More Help?

The CHOICE diabetes education programme is available in NI and the border counties of Republic of Ireland, ask your Diabetes Team

Choice Programme