If you've been diagnosed with diabetes, it's very important that you follow all recommendations regarding diet, medication, insulin therapy and self-testing to help prevent diabetic ketoacidosis.

You should also take extra precautions while you're ill, because illness can cause your blood sugar level to rise or fall to dangerous levels. 

What to do while you're ill

If you need to take insulin to control your diabetes, you should have previously received instructions about looking after yourself when you're ill – known as your "sick day rules". Contact your diabetes care team or GP for advice if you haven't received these.

The advice you're given will be specific to you, but some general measures that your sick day rules may include could be to:

• keep taking your insulin – it's very important not to stop treatment when you're ill; your treatment plan may state whether you need to temporarily increase your dose
• test your blood sugar level more often than usual – most people are advised to check the level at least four times a day (see below)
• keep yourself well hydrated – make sure you drink plenty of sugar-free drinks
• keep eating – eat solid food if you feel well enough to, or liquid carbohydrates such as milk, soup and yoghurt if this is easier
• check your ketone levels if your blood sugar level is high (see below)

Seek advice from your diabetes care team or GP if your blood sugar and/or ketone level remains high after taking insulin, if you're not sure whether to make any changes to your treatment, if you develop symptoms of diabetic ketoacidosis, or if you have any other concerns.

Checking your blood sugar and ketone levels

Simple finger prick blood test devices can be used to monitor your blood glucose levels.

Your diabetes care team should advise you about the level you should aim for and when you need to adjust your treatment or seek medical advice, but generally a reading of 11 mmol/l or more is a sign that you're at risk of diabetic ketoacidosis and should check your ketone level if you feel ill.

Ketone levels can be checked using urine test strips available on prescription, although it can take a few hours for ketones to show up in your urine. Many newer blood glucose monitors are also able to monitor blood ketone levels more quickly. Your diabetes care team will be able to provide you with more information on this.

Again, you should be advised about what a dangerous level of ketones is, but generally a reading of 2+ or more on urine strips or 0.6 mmol/l or more in your blood is a sign that you're at risk of diabetic ketoacidosis.

Contact your diabetes care team or GP immediately if you have persistently high or rising blood sugar and ketone levels. Go to your nearest accident and emergency (A&E) department if you develop severe symptoms of diabetic ketoacidosis.