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How carbs interact with your body

Understanding how different carbs interact with the body is key to carb counting.

Jess explains the two main ways of counting carbs, and how to work with your healthcare team to match the amount of insulin you need to take.


Key points

Insulin works to lower blood glucose (blood sugar) levels after eating carbs, which is why it is important to match the amount of insulin you take to the carbs you eat. The insulin dose you need depends on the amount of carbohydrate you are eating and your insulin-to-carb ratio.

You can count the carbs in your food using the nutrition information label (if your food has one) or by using reference books or apps. Carbs can be counted in grams or as carbohydrate portions (CP).

Remember that the amount you are going to eat will probably be different to the serving size on the label, or in the app, so you need to do some math. Here’s how:

  1. By ‘total carbs per serving’. If the serving size on the label is 75g and you will eat 150g, multiply the total carb value by two. This will give you the total carb in your serving.
  2. By weighing out portions and using per 100g information. If there is 38g of carbohydrate per 100g and you weigh out your portion and it is 75g, multiply 38 by 0.75 to find the carb in your serve (28.5g).

Insulin to carb ratios

Your insulin-to-carb ratio is how many units of insulin you need to take for a set amount of carbs. They vary from person to person. Chat with your healthcare team to work out your unique insulin-to-carb ratio.

For example, you’re planning to eat 70g of carbohydrate. Your insulin to carbohydrate ratio is 1 unit of bolus insulin for every 10g carbohydrate. You will need to take 7 units of bolus insulin. The amount you take depends on other factors too. Things like blood glucose level, illness, or planned activity.

Slow-, medium- and fast-acting carbs

Don’t forget about the difference between slow-, medium- and fast-acting carbs and how they’re absorbed by the body. Slow-acting carbs are absorbed very slowly and may not need to be matched with insulin unless eaten in large quantities. You’ll need to monitor your blood sugar levels to see the impact these foods have on you – and, of course, speak to the experts to find a method that best suits you.

And remember to eat a healthy balanced diet. Try reducing saturated fat, sugars, salt, and make sure you eat plenty of wholegrains, fruit, veg, and low-fat, low-sugar dairy.

"Buy a set of good digital scales to weigh your carbs – more accurate measurements mean you can have the right amount of insulin and hopefully less hypos and hypers.”

Claire, who has type 1 diabetes

Continue learning


3. What to look for on food labels video

These days, food labels should have all the key nutritional information you need to count the carbs in your meal. Find out what to look for on food labels, with tips and advice from Jess along the way.

Find out what to look for on food labels, plus tips and advice from Jess

Find out more

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