Managing diabetes when you're ill

Knowing how to adjust your routine if you’re taken ill can help you feel more in control, so you can focus on recovering.

Being unwell is never fun, but when you have diabetes, trying to manage your glucose can make any illness more complicated. When you have an infection, a fever, a stomach upset or a virus like a bad cold or flu, your body releases more glucose to fight the illness, producing spikes in your glucose levels.1

But if you are vomiting, insulin levels may run low and your body may start to break down fat for energy instead. This can lead to a rise in the production of ketones, which can develop into diabetic ketoacidosis, a life-threatening medical emergency.2

The best time to talk about being ill is when you’re well, at your regular diabetes appointment. You could discuss a ‘sick day care plan’ with your care team, who can advise on how best to look after yourself when you’re ill.3 This might include a number of ‘sick day rules’, such as:1

  • Test your glucose levels more often than usual to keep track.
  • If you use insulin to manage your diabetes, test your blood or urine for ketones if your blood sugar level is 15mmol/l or more, or 13mmol/l if you use an insulin pump.
  • Stay hydrated by drinking plenty of sugar-free liquids and avoiding alcohol.3
  • Try to eat regularly. If you can’t face food, have small portions of sugary foods or drinks.
  • Don’t stop taking your insulin or other diabetes medication, though you may need to adjust the dose – ask for help if unsure.
  • Avoid strenuous exercise, which can raise your glucose levels when you’re ill.3

When to ask for help

If you start to feel unwell and are unsure what to do, it’s much better to contact your GP or diabetes care team for advice, rather than struggle on and risk making yourself worse.1

Seek medical help urgently if:3

  • You can’t keep food down for four hours or more
  • You have continuous diarrhoea and vomiting
  • Your glucose levels are persistently high (above 15mmol/L)
  • Your blood or urine shows high levels of ketones

Be prepared

Keeping a ‘sick day kit’ at home could prove useful if you’re taken ill and don’t feel like going out to the shops. You could include3:

  • Small cartons of long-life fruit juice
  • Small bottles of full-sugar drinks
  • Cans of soup
  • Ice cream
  • Small packets of sugary sweets (eg jelly babies)
  • Valid ketone testing strips
  • Contact details for your diabetes care team, including emergency number


1. Diabetes 2019, Diabetes and being ill, accessed 15 March 2019,

2. NHS 2017, Diabetic ketoacidosis, accessed 15 March 2019,

3. Diabetes Research & Wellness Trust/ University Hospital Southampton NHS Foundation Trust/Managing diabetes when you are ill, accessed March 15 2019.



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