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Sickness and type 1 diabetes

When you get a bug or a virus, you might need to manage your type 1 diabetes a bit differently.
Content last reviewed and updated: 13.03.2024

A young guy with type 1 diabetes who is experiencing sickness and is blowing his nose

What happens when you get sick and you have type 1 diabetes?

If you get ill with a virus like the flu or a bacterial infection, your body will make and release stress hormones. These hormones can trigger a release of glucose that is stored in your liver. On these days your body will need more insulin.

What should you do if you become ill?

Being ill can make your blood glucose levels rise, so it’s important to check your blood glucose levels more, so you take the right amount of insulin.

If you don’t have enough insulin, your body starts to burn fat to make energy. This can produce ketones which can build up and make you even more unwell and even lead to more serious conditions like diabetic ketoacidosis (DKA).

You can help avoid this by regularly checking your blood glucose levels.

Type 1 diabetes and stomach bugs

You are less likely to produce stress hormones if you have a stomach bug, like gastroenteritis or norovirus. In this case your blood glucose levels are more likely to be low because you’re not eating or not absorbing the food that you are eating.

If you have vomiting or diarrhoea, follow the sick day rules below.

Do all illnesses affect blood glucose levels?

Not all illnesses have an impact on your blood glucose levels. Illnesses like chicken pox, seem to have little or no effect on your blood glucose. The impact of illness is very much dependent on the illness you have and can be different each time you have it.

Whatever illness you have, following the sick day rules will help keep you safe.

Sick day rules

  • Check your blood glucose regularly, at least every four hours.
  • Don’t stop taking your insulin , even if you’re unable to eat. You may have to take more insulin to balance out any rise in blood glucose levels caused by your illness.
  • Keep hydrated as dehydration can cause blood glucose to rise.
  • Eat little and often, especially if you’re struggling to keep food down. If you need to raise your blood glucose levels, sip sugary drinks or chew glucose tabs or jelly babies.
  • Check for ketones. Use a ketone monitor to measure and monitor ketones, every four hours. If you have any concerns, speak to your Diabetes Healthcare Team.

You can download the sick day rules so you have them to hand when you’re ill.

If you are unable to monitor your blood glucose and ketone levels as often as needed, contact your Diabetes Care Team.

Free vaccines

Generally, flu is an unpleasant virus which people usually recover from within two to seven days. However, if you’ve got type 1 diabetes the risk of a more serious illness developing is higher.

That’s why everyone with type 1 diabetes is eligible for a free flu vaccination. These are normally available from early autumn. Contact your GP or visit the NHS website to book your appointment.

If you have type 1, you will also be eligible for a COVID booster vaccination. Find out more on the NHS website.

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