What is my insulin to carbohydrate ratio and why is it important ?

We’ve all been there... We think we have the perfect insulin to carbohydrate ratio and then...surprise ! Your blood sugar either drops or increases unexpectedly and you are left feeling confused and angry.

What could be happening? Did I make a mistake in my calculation?

More often than not, you didnt. It could be that you are more insulin sensitive at certain times of day than others (this is usually seen in those with type 1 diabetes) or it could be that there is a change in your counter-regulatory hormones which increase insulin sensitivity (such as cortisol, adrenalin, etc).

Blood sugar values are so much more than the amount of carbs you eat and the medication you are taking. Sometimes, you can find patterns and make corrections. But othertimes, there may be no rhyme or reason as to why your blood sugar rose/plummeted. Check your knowledge of carb counting and know you are doing your best to control this complex disease !

What is an insulin to carb ratio (ICR) ?

Insulin to carb ratio represents how many grams of carbohydrates 1 unit of insulin will cover.

Who may benefit from an insulin to carb ratio?

People who are on multiple daily injections (MDI) would benefit from using an insulin to carb ratio at mealtime. If you are taking oral medications, you do not need to calculate your insulin to carb ratio. Those that are both on oral medication and insulin therapy may benefit from knowing their ICR however it will not be as accurate as there is also the lowering effect of the oral medications that cannot be taken into account in the calculation.

How do I calculate my insulin to carb ratio?

You take your total daily dose of insulin (TDD), this includes both long acting and mealtime insulin, and divide it by 450 if you are using short acting insulin (Humulin R or Novolin R). If you are using rapid acting insulin (Novolog or Humalog) then you would divide it by 500. These are called the 450 and the 500 rule respectively.

Example 1 : Levemir 23 units two times a day & Novolin R 6 units two times a day

TDD = (23x2) + (6x2) = 58

450/58 = 7.75g <— This means that for every ~8g of carbohydrates eaten, you need to take 1 unit of Novolin

Example 2: Basaglar 40 units a day & Novolog 4 units before each meal, three times a day

TDD = 40 + (4 x3) = 52

500/52 = 9.6g <— This means that for every 9.6g of carbohydrates eaten, you need to take 1 unit of Novolog

Remember to discuss your ICR with your provider or your certified diabetes educator before making any changes to your diabetes management. If you notice that your blood sugar does not return to normal levels after eating, check your carbohydrate counting and speak to your diabetes educator to make adjustments in your medications.