What’s a Correction Factor? An insulin sensitivity? A ratio?

A Correction Factor (sometimes called insulin sensitivity), is how much 1 unit of rapid acting insulin will generally lower your blood glucose over 2 to 4 hours when you are in a fasting or pre-meal state. However, you should keep in mind:

• this is an estimate

• it may need to change as your baseline dose changes

• expect variations - sometimes 1 unit will lower it by more, and other times 1unit will lower it by less!

• calculating how much 1 unit of insulin will drop your blood sugar is a trial and error process, and sensitivity to insulin varies with the individual

To get your total daily dose, add up all your usual meal time insulin and basal insulin. For example, Tom wants to calculate his correction factor:

1. daily insulin dose: 8 units at breakfast, 6 units at lunch,10 at dinner and N/NPH 8 units at breakfast and 18 units at 10 pm
2. Total Daily Dose (TDD) = 8 + 8 + 6+ 10 + 18 = 50
3. Correction Factor (CF) = 100/50 = 2

Therefore, one unit of rapid acting insulin would lower Tom’s blood sugar by 2 mmol/L over the next 2 to 4 hours.

The average adult needs approximately 1 unit of insulin for every 2 mmol increase in blood sugar, but this can vary a lot between individuals:

• some people need 1 unit of insulin for every 1 mmol/L increase in blood sugar
• others need 1 unit of insulin for every 3 -5 mmol/L increase in blood sugar

Using your CF before meal doses

Before meal means there has been about 4 hours or more since you last ate or took an insulin dose for carbohydrate containing food or beverage.

The correction factor or insulin sensitivity can be used to make a scale for pre meal insulin doses.

Example: If your baseline dose of insulin at breakfast is 4 units and your before breakfast blood sugar is 10.5 mmol/L, and your food and activity will be the usual, you need to take 6 units (4 units to cover your food and 2 units to correct for the high blood sugar).

Others do not write out their scale; they just calculate an extra dose using their Correction Factor and add it to their baseline (usual) dose at meals. With this method people need to remember their target blood sugar level. Subtract the target blood sugar from the current sugar to calculate the gap. Then divide by the Correction (sensitivity) Factor to calculate the correction dose. Discuss your target levels with your health care team (see Question 1).

Example:
Using the Correction Factor or insulin sensitivity

Target blood sugar is 7 & glucose is 13.2 before lunch

• baseline dose: 10 units
• Correction Factor: 1 unit â blood glucose 2 mmol/L

• 13.2 – 7 = 6 mmol above target
• 6 mmol divided by correction factor of 2 = 3 units to lower blood sugar by 6 mmol/L
• baseline of 10 + 3 for correction = 13 units
• therefore, the insulin dose would be 13 units with lunch

Using a CF to correct a 2 hour post meal blood sugar

Correcting for a high blood sugar 2 hours after eating is using your best estimate!

Things to consider:

• how your insulin works
  
• the type of meal you ate - high fat carbohydrate meal vs. high fibre, low fat carbohydrate meal
  
• is it the type of meal that makes your blood sugars higher than usual for a longer than usual time, or
  
• is it the type of where your blood sugars return to normal within the 2 hours

Remember how your insulin works – insulin action or duration of effect.

Rapid acting (Humalog or NovoRapid)

• starts: 10-15 minutes
• works strongest: 1 to 2 hours
  
• out of your body: 4 to 5 hours

At 2 hours approximately 50 to 60 per cent of your bolus is used. There still is about 50 to 40 per cent of that dose remaining to lower blood sugars. If you take the same correction bolus as you would before a meal, you may have a low blood sugar from ‘insulin stacking’!

To correct for high blood sugars at 2 hours after a previous bolus, estimate what you would use as a correction factor and then divide by 2 – or use your insulin pump calculator!

• Correction Factor: 1 unit â blood glucose 2 mmol/L
• target glucose is 10
• Blood glucose = 18.6 at 2 hours after breakfast
• 18.6 – 10 = 8.6
• 8.6 mmol/L divided by Correction Factor of 2 = 4
• 4 units will lower blood sugar by 8 mmol/L
• 4 divided by 2 = 2
• therefore, the 2 hour correction dose would be 2 units