Carbohydrate counting and dose adjusting

You have been started on 2 different types of insulin:

1. Novorapid (insulin aspart) - fast acting insulin which is used to cover the carbohydrate in the food you eat
2. Lantus (insulin glargine) - long acting insulin, which lasts 24 hours and provides you with a background of insulin throughout the day.

Understanding why you use this type of insulin programme will help to understand why it’s important to do “carbohydrate counting”.

For someone without diabetes, the amount of insulin the body makes is dependent on when and how much food is eaten.

For those with diabetes, the combination of long acting and short acting insulin tries to copy the way the pancreas would normally release insulin.

There are 5 steps to carbohydrate counting and dose adjusting.

The 5 steps are described below in more detail.  This video talks through each of these steps using several worked examples for how to calculate a mealtime bolus.

Split your meal up into the different food groups and look for sources of carbohydrate.
Using the table below you can see an example of a food diary with the carbohydrate sources identified.

There are lots of resources available to help you calculate the carbohydrate in your meal and it is about finding the easiest method for you and your family.

• Food Labels:  Using food labels is an accurate way of telling how much carbohydrate is in your food but is only really an option if you eat mostly ready made meals.
• Weighing Food:  Weighing food is the most accurate way to calculate carbohydrate but this can be difficult as it requires a lot of maths and is time consuming. The food is weighed and then the carbohydrate is counted by using carbohydrate reference tables.
• Carbs and Cals Book:  This provides pictures of food and tells you the carbohydrate content of various portion sizes. There is also a carbs and cals app available for smartphones.

1 unit of insulin covers a certain amount of carbohydrate - this is called your insulin to carbohydrate ratio (ICR). 
Your ICR will change as you grow and develop. You may also find that you might need different carbohydrate to insulin ratios depending on the time of day.

If your blood glucose level is higher than the target range (4-7mmol/l). then you need extra novorapid. This is called a correction dose.

After you have completed each step you inject the calculated dose of novorapid. This is called an insulin “bolus”.

Before giving your novorapid to cover the carbohydrate in your meal you should think about factors which may change the rate in which the insulin works. There are a number of things that can affect this including illness and exercise and what you are eating. Fat slows down digestion, so it takes a long time for the carbohydrate in your meal to turn into sugar.

If you have a fatty meal it might be worth splitting your insulin dose. This would mean calculating how much insulin you need for your meal and giving ½ of the insulin with your meal and the remaining ½ 90 minutes- 2 hours after your meal.

Examples of fatty foods that might need to be covered by two insulin injections:

• Food from a fish and chip chop
• Pizza
• Foods from takeaway e.g. Chinese/ Indian

Following all of these steps sounds like a lot of maths and calculations but this can all be done automatically by your blood glucose meter. The DOT team will set this up for you and teach you how to use it.  
Some people prefer to look at reference tables to help them decide upon a mealtime bolus.  A "ready reckoner" table can help calculate insulin for carbs, and a sensitivity table can be used to decide whether or not an additional correction dose is needed.  Ask the DOT team to advise you which sensitvity table is the correct one for you to use.
This video describes how to use these tables in more detail.