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Carbohydrates and diabetes: What you need to know

Many of us rely on carbohydrates as our main source of energy. Carbohydrate-containing foods also provide important nutrients for good health.

All the carbohydrates you eat and drink are broken down into glucose. The type, and amount, you consume can make a difference to your blood glucose levels and diabetes management.

There are different ways to describe carbohydrates. One way of doing this is to group them into those that contain mostly starch (such as bread, rice, pasta, potatoes, yams, plantain, breakfast cereals and couscous), and those that contain mostly sugars, such as fruits (fructose), some dairy foods (lactose), sweets, chocolate, sugary drinks and desserts. 


This is another type of carbohydrate, which you can’t digest. These are found in wholemeal bread, brown rice, wholegrain cereals, fruits and vegetables, nuts and seeds, pulses, potatoes, oats and barley. 

Fibre helps keep our digestive system healthy, and can also help to keep your blood glucose and cholesterol under control.

Make sure you eat enough fibre every day as this is associated with less risk of cardiovascular diseases and certain types of cancers. 

How much carbs?

Everyone needs some carbohydrate-containing foods in their diet. The actual amount that you need to eat will depend on your age, activity levels and the goals you are trying to achieve. For example, one person trying to lose weight and manage their blood glucose levels on a low-carb diet would restrict their carb intake, while another person who is happy with their weight may decide to eat more healthy carbs. The total amount of carbohydrate eaten will have the biggest effect on your glucose levels after eating, so it is important to know how much you’re eating. However, not everyone with diabetes needs to restrict their carb intake.

Knowing how many carbs are in your food

If you’re living with diabetes, and take insulin, you’ll need to take that into account when eating carbs. Learn about which foods contain carbohydrates, how to estimate carbohydrate portions and how to monitor their effect on blood glucose levels.

There are special courses available, such as the DAFNE course for people with type 1 diabetes, which your diabetes healthcare team can tell you about.

Our downloadable PDF e-book, Carbs Count, provides an introduction to carbohydrate counting and insulin dose adjustment. It takes you through the essential information, with practical examples and exercises. You can download Carbs Count for free through our online shop.

What about the quality of carbs? 

Evidence shows that the quality of the carbohydrates is more important to general health than the amount we eat. Quality of carbs has been assessed using glycaemic index (GI), glycaemic load, fibre content and wholegrain among others. Generally, lower GI foods can be useful for managing blood glucose levels. More importantly for overall health, choosing foods that are high in fibre and wholegrains instead of refined carbs, such as white bread, is better for our heart health and reducing our risk of certain types of cancers. We also know that some specific carb-containing foods, such as fruits and vegetables, are associated with good health. 

Ways to include good quality carbohydrates in your diet:

  • Choose wholegrain breads and cereals.
  • Have fruit whole, rather than as a juice. Eating an apple with the skin on, for example, will provide more fibre than drinking a glass of apple juice.
  • Ring the changes with quinoa and bulgur wheat as an alternative to pasta.
  • Try seeds, nuts and pulses as lower carb sources of fibre 
  • Choose unsweetened milk and yogurts

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. This means estimating how much carbs are in the individual foods and meals you eat in order to get the amounts right. 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 by injecting several times a day, or through a pump, you can be much more flexible in how much carbs you eat and when you eat. 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’re eating. Other factors are also important, such as any physical activity you have done or plan doing, any previous episode of hypos, any infections.

How does carbohydrate affect anyone with type 2 diabetes?

For people with type 2 diabetes who may be overweight or obese, reducing the calories you eat helps to lose weight. This can be done through different means including following a low carb diet or simply reducing the current amount of carbs you eat. People have successfully followed low carb diets to lose weight and manage their diabetes including lowering their HbA1c, cholesterol and blood pressure levels as well as reducing the amount of diabetes medications they take. If you are taking diabetes medications that put you at risk of hypos, checking your blood glucose levels regularly and speaking to your healthcare team to review your medications will help to reduce your risk of hypos when you restrict your carb intake.

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