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Carb counting

Carb counting is working out how much carbohydrate is in your food so you can work out how much insulin to take. Learn how to count carbs, which apps can help, which courses are available to help you learn, and what you need to consider when eating out.
Content last reviewed and updated: 16.05.2024

A woman cooking pasta at home where she can carb count to manage her diabetes

What is carb counting?

Carb counting is working out how much carbohydrate is in your food and adjusting your insulin dose accordingly. You need to know this so you can take the right insulin dose after you eat or drink something with carbs in it. This page tells you how to count carbs, work out how much insulin you need and how to get help with carb counting.

Why do you need to count carbs when you have type 1 diabetes?

When you eat or drink carbohydrates (known as carbs), your body breaks them down into glucose to give you energy. In someone who doesn’t have type 1, the beta cells in the pancreas would then release insulin to stop the levels of glucose (sugar) in your blood going too high. If you have type 1, those cells don’t release insulin so you have to put it into your body yourself, either with injections or an insulin pump.

You need to know how many carbs you’re eating so that you can take the right dose of insulin to stop your blood glucose levels going too high (by not taking enough insulin) or too low (by taking too much insulin).

It can feel like there’s a lot to learn, especially with the other aspects of managing type 1. Take your time, don’t expect to get everything right straight away. Ask your Diabetes Healthcare Team for help and support when you need it.

What kind of carbs are there and what do I need to count?

There are two main types of carbohydrate that you need to be aware of when you have type 1 diabetes:

  • starches (potatoes, peas, beans, rice and grains)
  • sugars (natural sugars in fruit or milk or added sugar in cakes and cookies)

These carbohydrates are released into the bloodstream differently. Starches release slowly over time so the rise in blood glucose will be more gradual. Sugar releases more quickly, so will cause more of a spike in blood glucose levels.

How do you count carbs?

Food labels

Every food that comes in packaging has a nutritional information label. This tells you how many carbohydrates the food contains. Labels often break down the carbohydrates into fibre or sugars, but the information you need is the total carbohydrate.

You can also find this nutritional information on supermarket websites.

Weighing and measuring your food

You might need to weigh your food so that you can get the right information from the label.

Make sure you read the information carefully – most labels have values ‘per 100g’ and/or ‘per portion’ so make sure you get the right one.

For example, on this label for a loaf of bread, if you were to eat just one slice you would be eating 20g of carbohydrates. But if you were eating 75g of bread, you would be consuming 34g of carbs (75g is 75% of 100g, so 75% of 45.5g would be 34g).

A food nutrition label that can be used to help with carb counting

If serving sizes are given in volume, like litres or millilitres, use a measuring cup to find out how much you’re eating or drinking.

Some food labels are per packet – like yogurt or crisps for example – so you won’t have to weigh this out separately.

At first this might feel like a lot of effort, but in time you will be able to visualise and estimate how many carbs are in the foods you’re eating – especially if they’re your favourites and you have them often.

Using apps

There are apps that can make carb counting a lot easier especially when food doesn’t have labels.

Apps like Carbs and Cals and My Fitness Pal have databases of the nutritional information for thousands of foods. Their databases also contain nutritional information for restaurant chains and food brands which can make eating out or on-the-go much easier. Find out more about these apps.

A group of women eating out and carb counting

Carb counting and eating out

Eating out at a restaurant, at a friend’s or ordering a takeaway can make carb counting tricky, but it doesn’t mean you can’t enjoy eating and socialising at the same time.

If you’re going to a restaurant, look online to see if they have any nutritional information on their website. If they don’t have specific nutritional information, you might be able to decide what meal you’re going to have in advance so you can try and work out the carbs.

Some apps have popular restaurant chains in their databases, so you can use them to look up how many carbs are in their meals.

If you’re eating at a friend’s house, you can ask them in advance what they’re making or ask them to share the recipe with you.

Remember that if you’re eating out your meal may be served late, and the portion sizes are likely to be different to those you have at home. Consider calculating your insulin on the minimum amount of carbs you expect your meal to contain. You can then reassess when the food arrives and top up your insulin if needed – but remember to keep something handy in case the food is delayed.

Working out how much insulin to take

To work out how much insulin you need to take, you’ll need to know your insulin to carbohydrate ratio. Your Diabetes Healthcare Team will tell you what your ratio is.

Doing the maths

Carb counting and making calculations can be tricky at first. Don’t worry if you’re not good at maths, over time you will get used to how many carbs are in certain foods especially if they’re your favourites and you eat or drink them often.

We’ll assume that your Diabetes Healthcare Team has told you that your insulin to carbohydrate ratio is 1 unit of insulin for every 10g of carbs you eat.

A food label to help with carb counting

You’re going to eat a portion of this pasta. The label tells us that a portion contains 43g of carbs.

To work out how much insulin you need, divide the number of grams of carbohydrate you’re eating (43g) by 10 (this is the 10g in your ratio).

Then multiply this answer by the number of units you need to take for every 10g of carbs, in this case, it’s 1.

So you need to take 4.3 units of insulin to cover the carbohydrates in this portion of pasta.

Bear in mind that the pasta here is only one ingredient – you’d have to also calculate the carbs in anything you have with it.

Carb counting and insulin pumps

Insulin pumps and hybrid closed loop systems can make carb counting easier because you can enter the amount of carbs you’re going to eat and it calculates how much insulin you need. Find out more about insulin pumps.

How do I know if I’m getting carb counting right?

A good way to see if you’re on the right track is to check your blood glucose before you eat and then several hours after eating. This will help you see if your estimate was right.

Don’t worry too much if you’re not getting everything right all the time – you’re only human and carb counting is not always an exact science. Remember that other things can affect your blood glucose levels as well as carbs, like doing exercise, being unwell or being too hot or cold.

If you’re struggling with carb counting – or any aspect of your type 1 management – ask for help. You don’t have to manage it all on your own so speak to friends, family and your Diabetes Healthcare Team.

Carb counting courses

There are courses you can attend that help you learn how to count carbs, such as the Dose Adjustment for Normal Eating, known as DAFNE, and BERTIE Online. Find out more about diabetes education courses.

The Roche Accu-Chek Carbohydrate Counting Tool provides free online training counting carbs (you don’t have to use an Accu-Chek pump or meter to use the tool).

Carb counting and pregnancy

If you’re pregnant or planning a pregnancy it can be useful to update your carb counting skills. This is because, during pregnancy, tighter management of blood glucose levels is important. Find out more about type 1 diabetes and pregnancy.

Do I need to eat healthily all the time?

A well-balanced diet is good for everyone – whether they have type 1 diabetes or not. But there’s no need to cut out tasty treats, as long as you adjust your insulin dose to cover any extra carbs. Find out more about food and nutrition.

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