The rules for sick days

Diabetes nurse educator, Kate Bristow, outlines the rules for sick days and how to manage diabetes when you are sick.

COVID-19 has made the whole world sit up and take note but if you have diabetes, it is useful to know a bit more about handling sick days and the higher blood glucose readings that go with it, no matter what the cause of illness is.

When you are sick, your body will make a hormone called cortisol which is a stress hormone. Cortisol increases resistance to insulin which forces your liver to make more glucose, resulting in higher blood glucose levels. These signs are increased urination and thirst.

In some cases, the cells of your body will keep looking for something to give them energy and they will break down fat. Fat is converted to ketones by your liver. Ketones are toxic or poisonous to our bodies. Some signs of ketones can be tummy aches, nausea, and vomiting.

Which illnesses may affect your diabetes and your glucose levels?

  • Common colds/flu – this now includes COVID-19
  • A sore throat
  • Infections of the urinary tract
  • Chest infections/bronchitis/pneumonia
  • Gastric/stomach upsets
  • Skin infections e.g. abscesses

Be aware that certain medications used to treat infections may also impact the blood glucose levels. Cortisone treatment commonly used will cause the blood glucose levels to increase significantly.

How to deal safely with sick days

  • Know your targets – expect an increased blood glucose level and discuss how to handle this in advance with your healthcare team. Elderly patients with diabetes will have slightly higher targets – targets are individualised with your diabetes nurse educator and your doctor.
  • Understand how to adjust your medication and when to call the healthcare team for help.
  • Test your glucose levels more regularly. It’s recommended every two to four hours, including during the night. This applies to patients taking tablets and those on insulin and/or tablets.
  • If you take insulin you may need to test for ketones as well. Your healthcare team will help with this.
  • There is no need to eat when you are sick, but it is important to stay hydrated. High blood glucose levels will make you thirsty and urinate more often, this can lead to dehydration which is equally bad for your system. So, drink more often, even just small sips.
  • Keep taking your insulin as normal, you may need more not less.
  • Some medications may be stopped in infections, these include metformin and SGLT2 inhibitors. Discuss this with your healthcare professional.
  • Check all over-the-counter medications with your pharmacist but they are generally okay, even if they contain a bit of sugar.
  • If you have ketones, anti-nausea medications may not be effective.
  • If you have extremely high blood glucose levels and are on insulin, know the symptoms of ketone build up: tummy ache, nausea and vomiting.
  • Rapid breathing with no cough or fever as well as vomiting without diarrhoea could indicate an increase in ketones.
  • If you can’t keep fluid down or have anything that makes you worried, call for help. A lot of assistance can be given on the phone.
  • Have the contact details for your healthcare team on the fridge and easily accessible to your family/support system. It is okay to ask for help.


High ketone levels are called diabetic ketoacidosis or DKA.

High ketone levels are called diabetic ketoacidosis or DKA.

Essential supplies to manage your glucose levels

  • Blood glucose test kit
  • Glucose test strips
  • Basal and rapid-acting or mixed insulins (as prescribed)
  • Oral medications (as prescribed)
  • Quick-acting carbs/sugars to treat a low if necessary
  • Ketone test kit and ketone strips
  • Glucagon
Sister Kate Bristow is a qualified nursing sister and certified diabetes educator.


Kate Bristow is a qualified nursing sister and certified diabetes educator. She currently runs two diabetes clinics as well as consults with patients privately, on a one-on-one basis via their medical aids, providing the network support required and on-going assistance and education to assist them with their self-management of their diabetes.

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