Diabetes and illness

It is very important to know how to cope with illness if you have diabetes or know or care for somebody with diabetes. If in doubt, always seek advice from your doctor or nurse straightaway.

Any illness or other type of stress will raise your blood sugar (glucose) levels, even if you are off your food or eating less than usual. People with diabetes are unable to produce more insulin to control the glucose level. The increased glucose level can make you become very lacking in fluid in the body (dehydrated).

Acting quickly and following advice helps to keep your glucose levels in the normal range or only slightly high. Because it can sometimes be very difficult to control your blood glucose levels, treatment in hospital may be needed. Hospital treatment may also be needed if you become very dehydrated.

Sick day diabetes guidelines

The following guidance is provided by Diabetes UK:

• Contact your general practice or diabetes team who will help you if you have any queries or if you are unsure about what to do.

• In general, you should keep taking your diabetes medications, even if you don't feel like eating. But there are some medicines that you shouldn’t take as much of or you should stop taking altogether. See the section below on 'Sick day rules diabetes type 2' for further information. Make sure you talk to your diabetes team or speak to a local pharmacist as soon as you’re feeling ill so they can give you the right advice.

• Insulin may need to be increased or decreased when you're unwell. Again, talk to your diabetes team for further advice on how to manage your insulin doses during illness.

• If you check your blood sugars at home you'll probably need to do it more often – at least every four hours, or as advised by your healthcare team, including during the night. If you don't test your blood sugars at home, be aware of the symptoms of a high blood sugar (hyperglycaemia), which may include feeling very thirsty, passing much more urine than usual, feeling weak or tired, and blurred vision.

• Keep eating or drinking:

  • if you can’t keep food down try eating little and often. Try snacks or drinks with carbohydrates in to give you energy. Try to sip sugary drinks like fruit juice or non-diet coke or lemonade or suck on glucose tablets or sweets like jelly beans.

  • Stay hydrated – drink plenty of water.

  • If you are being sick letting fizzy drinks go flat may help keep them down.

  • If you're still not able to keep any fluids down get medical help as soon as possible.

There are things you can do to protect yourself against some illnesses. This includes getting your influenza vaccine and covid booster every year. And it may sound simple, but avoiding people who are sick and washing your hands often and thoroughly can help to protect yourself and others too.

Further information on managing diabetes during a period of illness is available on the Diabetes UK website (see Further Reading below for the link).

There is also further information in the following sections on Type 1 diabetes and Type 2 diabetes.

Sick day rules diabetes type 2

• Although the general rule is to keep taking all medicines, some medicines may need to be stopped during acute illness. Always contact your diabetes team or general practice for advice, including whether you should temporarily stop any medicines while you are unwell. Medication may be restarted once you are feeling better and eating and drinking for 24–48 hours, unless there is concern about how well your kidneys are working.

  • On angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (azilsartan, candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, valsartan), diuretics (thiazide diuretics or loop diuretics), or anti-inflammatory tablets: stop treatment if there is a risk of severe loss of fluid from the body (dehydration), to reduce the risk of kidney problems (acute kidney injury).

  • On metformin: stop treatment if there is a risk of dehydration, to reduce the risk of lactic acidosis.

  • On sulfonylureas (gliclazide, glimepiride, glipizide, tolbutamide): may increase the risk of low blood sugars (hypoglycaemia), particularly if dietary intake is reduced.

  • On SGLT-2 inhibitors (canagliflozin, dapagliflozin, empagliflozin, ertugliflozin): may need to be stopped if acutely unwell or at risk of dehydration, due to the risk of diabetic ketoacidosis, which can be life threatening and needs urgent treatment in hospital.

  • On GLP-1 receptor agonists (dulaglutide, exenatide, liraglutide, lixisenatide, semaglutide): treatment should be stopped if there is a risk of dehydration, to reduce the risk of acute kidney injury.

  • If on insulin therapy, do not stop treatment. The dose of insulin may need to be altered during periods of illness. Seek advice from the specialist diabetes team if there is uncertainty on how to adjust insulin doses.

For further information about the medicines listed above, see Type 2 diabetes treatment.

• If self-monitoring of blood glucose levels is required (for example on insulin therapy):

  • An increase in monitoring frequency may be needed, such as at least every 3–4 hours including through the night and record the results. Insulin doses may need to be adjusted, depending on the results.

  • Continue to self-monitor blood glucose levels carefully when feeling better, until they are back to the usual baseline.

  • Seek urgent medical advice if blood glucose levels remain uncontrolled.

• Maintain normal meal pattern (including fluids and carbohydrate intake) where possible if appetite is reduced.

  • If unable to eat or vomiting, replace normal meals with carbohydrate-containing drinks (such as milk, milkshakes, fruit juices, and sugary drinks).

  • If blood glucose levels are high, maintain fluid intake with sugar-free fluids.

  • If blood glucose levels are low, have a regular intake of sugary fluids.

Seek urgent medical advice if you are:

• Unable to eat or drink, or you are dehydrated or at risk of dehydration.

• Have persistent vomiting.

• Have low blood sugar levels (hypoglycaemia).

Sick day rules diabetes type 1

• During a period of illness that does not require admission, keep to the 'sick-day rules':
  Never stop or omit insulin. The dose of insulin may need to be altered during periods of illness. Seek advice from their diabetes team if they are unsure of how to adjust insulin doses.

• Check blood glucose and ketone levels more frequently, for example every 1–2 hours including through the night. The insulin dose should be titrated according to the blood glucose results and the written 'sick-day rules'.

• Also check urine ketone levels regularly, for example every 3–4 hours including through the night, and sometimes every 1–2 hours depending on results. If the urine ketone level is greater than 2+, contact your diabetes care team immediately.

• Maintain normal meal pattern (where possible) if appetite is reduced. Normal meals can be replaced with carbohydrate-containing drinks (such as milk, milk shakes, fruit juices, and sugary drinks).

• Aim to drink at least 3 L of fluid (5 pints) a day to prevent dehydration.

  • If blood glucose levels are normal or high, water or sugar-free fluids are probably most appropriate in the majority of cases.

  • If blood glucose levels are low, drinks containing glucose are required (or the person should take carbohydrates if possible).

  • Carbonated drinks should be avoided if possible.

• Seek urgent medical advice if you're violently sick, drowsy, or unable to keep fluids down. Intravenous fluids in hospital may be required.

• When feeling better, continue to monitor blood glucose carefully until it returns to normal. This may take some time.

• Seek medical advice if your blood glucose remains uncontrolled.

See also the article on Type 1 diabetes.

Frequently asked questions

What happens to my diabetes when I am unwell?

When a person with diabetes is unwell the sugar level in the blood tends to increase. This can happen even with a very mild illness such as the common cold. The blood sugar (glucose) may go up even if you are not eating properly or are being sick (vomiting) or have loose or watery poo (diarrhoea). The increase in blood sugar may make you very lacking in fluid in the body (dehydrated).

When should I contact a doctor or nurse for advice?

You should seek medical advice if:

• You live alone and have no support.

• You are unable to eat or drink.

• You are being sick (vomiting) or have loose or watery poo (diarrhoea).

• Your blood sugar (glucose) level is higher than 25 mmol/L.

• Your blood glucose level is very low.

• You have large amounts of ketones or persistent ketones in the urine. Ketones are made when you break down fat in your body.

• You become drowsy or confused (make sure carers, friends, neighbours and relatives are aware of this).

• You have any other concerns or feel unsure about what you should do.

What if I use insulin to control my diabetes?

• INSULIN SHOULD NEVER BE STOPPED. Your blood sugar (glucose) may go up when you are unwell, even if you are not eating much.

• You must check your blood glucose levels more regularly. You should check your blood glucose every four hours or even more often, including through the night. Your dose of insulin may need to be increased or reduced depending on your blood glucose levels. If you are not sure then contact your GP or diabetes specialist nurse for advice.

• You should also check your urine for ketones at least once or twice each day. Ketones are made when you break down fat in your body. Ketones may appear in the blood and urine due to starvation or because of a lack of insulin. The presence of ketones in the urine may be a warning of diabetic ketoacidosis.

• Diabetic ketoacidosis is a serious complication of diabetes. Large amounts of ketones are released into the blood. The high level of ketones causes blood acidity, which is harmful to the body. Ketoacidosis is a life-threatening emergency which needs to be treated quickly.

• Your dose of insulin should be put back to your usual dose when you are better and the blood glucose levels return to normal.

What should I do if I need to take steroid tablets?

Steroid tablets (for example, prednisolone) are very important for treating some illnesses, such as severe asthma. Blood sugar (glucose) levels may increase when you are taking steroids, especially steroid tablets or injections.

It is very important not to stop taking the steroids but you should check your blood glucose levels regularly. Always get advice from your GP if you have diabetes and need to take steroid tablets. Your GP may need to increase or change your diabetes medication while you are taking steroids.

People on long-term steroid medication need to have their own sick day rules. See the leaflet on Addison's disease for further information and discuss any concerns with your GP or hospital team.