The role of carbohydrates

The glucose circulating in your blood comes primarily from the carbohydrates (sugars) you eat. When you have diabetes, your body can’t properly use the energy circulating as glucose in your blood, which can raise your glycemia (the level of sugar in your blood) beyond normal values.

Nevertheless, people with diabetes should not eliminate carbohydrates from their diet: carbohydrates are the body’s main source of energy and the sole fuel for the brain.

A person with diabetes should not eliminate carbohydrates, but should monitor closely the amounts eaten and distribute them over three daily meals in order to control blood glucose (sugar) levels.

Sources of carbohydrates

Carbohydrates comprise all the sugars found in foods. They include sugars, starches and dietary fibre.

Sugar can be naturally present in foods or added to them:

  • Natural sugars: found naturally in milk and its alternatives, starchy foods, legumes and pulses, fruit and vegetables (in smaller amounts) and their juices, etc.
  • Added sugars: added to cookies, sweet drinks, candy, cakes and other processed foods.

Whether the carbohydrates come from a natural source or are added, they all break down into glucose to provide energy to the body’s cells. Therefore, they all have an effect on blood glucose (sugar) levels.

Simple or complex carbs?

Carbohydrates belong to one of two large classes:

1.  Simple carbohydrates: the most common are glucose (dextrose), fructose, lactose and sucrose. They are quickly absorbed by the body. They are found in:

  • fruits and their juices
  • milk and yogurt
  • sweet foods (pastry, chocolate, jams and syrups)
  • refined sugar (white sugar (sucrose), honey, molasses, maple syrup, etc.)

2.  Complex carbohydrates: these carbohydrates are composed of several glucose units joined in a long chain called starch. They are absorbed more slowly by the body and do not give foods a sweet taste.They are found in foods containing starch, often called starches:

  • bread
  • crackers
  • cereal
  • rice and pasta
  • legumes and pulses
  • potatoes

Dietary fibre also belongs to the class of complex carbohydrates but, unlike all other carbohydrates, it has no effect on blood glucose (sugar) levels because it is neither digested nor absorbed by the body.

Nutritional advice

Carbohydrates have a direct impact on blood glucose levels. That is why it is important to control the amount consumed and to evenly distribute their consumption throughout the day, over at least 3 meals.

You should choose carbohydrates that come from nutritious foods (rich in vitamins, minerals and fibre).

Nutritious, carbohydrate-rich foods are primarily:

  • grains (preferably whole grain – rice, pasta, bread, cereal, etc.)
  • vegetables and fruit
  • milk and certain milk products
  • legumes and pulses (chickpeas, lentils, etc.)

A variety of foods from these categories should appear regularly on your menu.

You can eat refined sugars on an occasional and moderate basis as part of a balanced meal containing other carbohydrates, proteins and fats.

When eaten as part of a meal, sugar has less of an impact on blood glucose levels.

For people with type 2 diabetes or those with a daily meal plan with predetermined amounts of carbohydrates for each meal, refined sugars, when eaten, must replace the other carbohydrate foods normally eaten and not be added to them. The total carbohydrate count must stay essentially the same from day to day.

If you buy processed foods, read the Nutrition Facts table and ingredient list on the package label to find the amount of carbohydrates.

Remember: a food with no added sugar is not necessarily carbohydrate-free because carbohydrates can be found naturally in foods (for example: unsweetened fruit contains natural fruit sugar).

Carbohydrate requirements

The amount of carbohydrates that a person requires each day depends on various factors:

  • age
  • gender
  • height
  • weight
  • physical activity

In general, most adults need between:

  • 45 g and 75 g of carbohydrates per meal
  • 15 g and 30 g of carbohydrates per snack, if needed

Note that adolescents, athletes and young adults with type 1 diabetes may have much higher daily carbohydrate needs.

Your dietitian will help you determine the amount of carbohydrates you need.

Low carbohydrate diets

Health Canada recommends that at least 45% of total energy (calories) should come from carbohydrates (sugars).

What about low carbohydrate diets that are between 4% and 45% of total energy? For more information on low carbohydrate (ketogenic) diets, please visit our web page by clicking here.

The ABC’s of Carbohydrates

Watch the following video presented by the Clinical Research Institute of Montreal (CRIM) for more information about carbohydrate (in French only)s:

Refences :

Galibois, Isabelle, (2005). Le diabète de type 1 et ses défis alimentaires quotidiens. Québec: Les Presses de l’Université Laval

Sievenpiper J, Chan C, Dworatzek P et al. Diabetes Canada 2018 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Nutrition Therapy. Can J Diabetes 2018; 42 (Suppl 1): S64-S79.

You can calculate carbohydrates with the simplified or advanced method. Which method you use will depend on your diabetes treatment, your motivation and your ability to apply the method.

The simplified method of calculating carbohydrates is used for a daily meal plan with a set amount of carbohydrates for each meal and snack. A dietitian will create your daily meal based on your needs.

Your intake of carbohydrates will be the same every day, just like the dosage of your antidiabetic medication or insulin. That is why you must calculate the amount of carbohydrates you’ve eaten to ensure that it matches the amount stipulated in your daily meal plan.

Know your sources of carbohydrates

First of all, you need to have a good knowledge of the sources of carbohydrates so you can easily identify them and include them in your carbohydrate counting.

Measure your serving sizes

We recommend that you use a measuring-spoon set and measuring cups to check the serving size of carbohydrate-containing foods. You can also weigh them on a kitchen scale.

Once you become familiar with those portions, you will be able to estimate the amount of carbohydrates on your plate at a glance without having to measure, especially when you’re eating out.

You can also use visual guides, like your hands, or the space taken by foods on your usual plate.

Calculate the amount of carbohydrates you eat at each meal

You must calculate the total amount of carbohydrates based on the portions you’ve eaten of each carbohydrate-containing food.

Here are a few tools for the simplified carbohydrate calculation:

  • Read the Nutrition Facts label

You can find the amount of carbohydrates in the nutrition facts table on the label of packaged food.

Remember to compare the reference serving size indicated on the label to the portion that you actually eat, and adjust your calculations accordingly.

Also, since fibre has no effect on your blood glucose (sugar) levels and is included in the carbohydrates total, you can subtract it.

  • Food components tables

You can find complete information about the nutrients and other components of many foods in Canadian Nutrient File (CNF) (Heath Canada, 2018).

  • Diabetes Québec’s exchange system

The exchange system developed by Diabetes Québec can help you estimate the carbohydrate content of most foods, including fresh fruits and vegetables, which don’t have Nutrition Facts labels.

In this system, foods from food groups containing carbohydrates are generally presented in serving sizes that provide 15 g of carbohydrates, which corresponds to one exchange.

Below is a sample carbohydrate counting for a meal using Diabetes Québec’s exchange system:

Rice150 ml or 2/3 cup2 starch exchanges30 g
Chicken breast90 g or 3 ouncesmeat and alternatives0 g
Olive oil5 ml or 1 teaspoonfats0 g
Cooked broccoli250 ml or 1 cup2 vegetables exchanges10 g
Plain yogurt175 ml or ¾ cup1 exchange of milk and alternatives15 g
Pear1 medium1 exchange of fruit15 g
Total carbohydrates in the meal:70 g

For examples of serving sizes equalling one exchange in each food group, consult these available resources above:

  • Meal Planning for People with Diabetes at a Glance
  • Meal Planning for People with Diabetes

Research and text: Diabetes Québec team of dietitians/nutritinists

July 2014 (updated on August 2018)

© All rights reserved Diabetes Québec


Ordre professionnel des diététistes du Québec (Professional Order of Québec Dietitans), “Meal plans based on the carbohydrates counting” (2007), Manuel de nutrition clinique. (Web page consulted July 22, 2014).

The advanced method of carbohydrates counting allows more flexibility in the amount of carbohydrates you eat at each meal.

This method is only for people whose diabetes is being treated with multiple daily insulin injections or an insulin pump, and who are already familiar with the simplified method of calculating carbohydrates.

The injected insulin dose at meals must be adjusted in accordance with the amount of carbohydrates eaten.

The insulin adjustment, determined by a healthcare professional, varies from person to person. It is based on an insulin/carbohydrate ratio that is dependent on a person’s sensitivity to insulin. There are two ways to describe this ratio:

  • A predetermined number of insulin units / 10 grams of carbohydrates
  • 1 unit of insulin / predetermined amount of carbohydrates

To learn more about the advanced carbohydrate-calculation method, download above:

  • Le calcul des carbohydrates – méthode avancée (1 unité d’insulin / n grammes de carbohydrates)
  • Le calcul des carbohydrates – méthode avancée (n unité d’insulin / 10 grammes de carbohydrates). (French only.)

Research and text: Diabetes Québec Team of Dietitians

July 2014 (updated on July 2018)

©All rights reserved Diabetes Quebec


Galibois, Isabelle, (2005), Le diabète de type 1 et ses défis alimentaires quotidiens, Québec: Les Presses de l’Université Laval

Ordre professionnel des diététistes du Québec (Professional Order of Québec Dietitans), “Meal plans based on the carbohydrates counting” (2007), Manuel de nutrition clinique. (Web page consulted July 22, 2014).