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Carb counting & insulin adjustment

Why does my body need carbohydrate?

Carbohydrate is the body’s preferred source of energy. All carbs are broken down into glucose - essential fuel for the body, especially the brain. High-fibre carbohydrates such as whole grains and fruit play an important role in the health of the gut.

Note: Some people with diabetes have wondered if it would be better not to have any carbohydrate in their diet to keep their blood glucose levels under control. This would be a mistake.

What is carbohydrate?

Carbohydrate can be classified in two main types:

  • Starchy carbs: foods like bread, pasta, chapattis, potatoes, yam, noodles, rice and cereals.
  • Sugars, such as: natural sugar, eg fruit sugar (fructose) and milk sugar (lactose), added sugar, which includes table sugar (eg caster, granulated), glucose, glucose syrup, invert syrup and honey.

Note: Both the amount and type of carbs you eat and drink will have an effect on your post-meal glucose levels. Sugars can often be identified on food labels as those ingredients ending in -ose. Another type of food that can affect blood glucose levels is nutritive sweeteners such as polyols - they tend to end in -ol, eg sorbitol, maltitol, xylitol and mannitol.


How much carbohydrate do I need?

  • The amount of carbohydrate the body needs varies depending on your age, weight and activity levels, but it should make up about half of what you eat and drink over the course of a week.
  • For good health most of this should come from starchy carbohydrate, fruits and some dairy foods. A small amount of your total carbohydrate can come from added sugar (table sugar). See Healthy eating for a clearer guide
  • All carbohydates affect blood glucose levels, so being aware of how much you are eating could help you to achieve good blood glucose control

Note: Work with your dietitian or diabetes healthcare team to find the right balance for you.


How does carbohydrate affect anyone with Type 1 diabetes?

All carbohydrate is converted into glucose. In someone without diabetes, the body produces insulin automatically to deal with the glucose that enters the blood from the carbohydrate-containing food that we eat and drink.

In Type 1 diabetes the same principle applies but because your body doesn’t produce any insulin, you have to take insulin, either by injections or a pump. This will help to lower the glucose in the blood after eating carbohydrate-containing foods. Most people follow twice-daily or basal bolus insulin regimes.

  • Twice-daily insulin
    If you are taking fixed amounts of insulin twice a day you may find it beneficial to have consistent amounts of carbohydrates on a day-to-day basis, and eat roughly the same amount of carbohydrate at similar times each day. More carbohydrate than usual can cause blood glucose levels to go too high, and less than usual can cause a hypo (low blood glucose levels).
  • Basal bolus insulin
    If you are using a basal bolus insulin regime or pump you can be much more flexible in how much insulin you take and when you take it. Most people following this regimen will count carbohydrates that they eat and drink and then calculate how much insulin they need to take. The amount of insulin will change depending on how much carbohydrate they have eaten.

Carb counting resources

The Carbs Count e-book has been developed by qualified diabetes dietitians and professionals, and provides background information on carbohydrates and how to carbohydrate count. It also covers the different types of insulin available, how they work and how each one should be adjusted according to what you eat, drink and the amount of physical activity you do. Available as a PDF e-book, Carbs Count can be downloaded for use. Go to our online shop to download the PDF for free.

Read your food labels

  • Double-check the measurements of the food item.
  • What is the portion or serving size?
  • The carbohydrate you count is the 'Total carbohydrate' rather than the 'of which sugars'.
  • Check if the amount of carbohydrate is for the raw or cooked product.
  • Consider what ingredients make up the product you are looking at. If it is a food that contains a lot of very slowly digested carbohydrates, such as beans or tomatoes, you would not count this carbohydrate. But the carbohydrate value will include them. Check the ingredients list to get a sense of how much of these foods are in the product.

E-learning programme from the Bournemouth Endocrine and Diabetes Centre

The Bournemouth Endocrine and Diabetes Centre have been running structured education programmes since 1999 to teach people with Type 1 diabetes on a basal bolus insulin regime how to match their insulin dose to the amount of carbohydrate they eat.

They have used their teaching materials to develop an interactive website, specifically designed to introduce the principles of carbohydrate counting and insulin dose adjustment. The site is ideal for people who wish to begin learning these principles for the first time, or as a refresher for people who need to update their skills.

Diabetes UK encourages you to visit the BDEC Diabetes Learning Programme site if you wish to learn more about carbohydrate counting.