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Sick day guidance for type 1 diabetes

This page describes what to do if you are sick and have type 1 diabetes.


If you have diabetes, it is very important that you know what to do when you are ill.

When you are ill your body becomes much more resistant to the insulin you produce or take by injection. This means that your blood glucose levels can rise and it is likely that you will need to increase your insulin dose. You therefore need to monitor your blood glucose and ketone levels very carefully. We refer to this as ‘sick day guidance’.

What could cause my blood glucose levels to rise?

The impact on your diabetes will usually depend on whether you have a minor or major illness.

Minor illness

This is when your blood glucose is either within the normal range or raised but with ketones in your blood or urine remaining negative (e.g. a minor viral infection or minor injury).

Severe illness

This is where your blood glucose is raised and ketones are positive in your blood or urine (e.g. a chest infection or another more severe infection). It may also be caused by missed insulin injections. Remember that testing positive for ketones is a sign that you are low on insulin.

For more information on this, see the flow chart for guidance.

It is important to remember that when you are ill, you must monitor your blood glucose levels closely and you should never stop taking your insulin, even if you don’t feel like it.

Managing your diabetes when you are ill

  • If you are vomiting, you do not need to eat until you feel well enough to try, but keep sipping fluids to prevent dehydration. You should drink at least 100 ml per hour.
  • If you do not feel like eating normal meals, try to eat foods that are easy to digest, e.g. soup, ice cream, milk puddings.
  • If your blood glucose falls below the normal range, sip full-sugar drinks, fruit juice, sweetened tea or Lucozade, or suck an ice lolly.
  • If you have an infection that is not clearing up, you should make an appointment to see your GP to determine whether you need further treatment.
  • If you continue to vomit, are unable to keep fluids down and/ or cannot manage to reduce your blood glucose or ketone levels you must contact the hospital as an emergency.
  • Adjusting your insulin doses will help to control your blood glucose levels (see the flow chart and below).

Insulin Adjustment

  • Extra insulin will correct hyperglycaemia and clear ketones
  • Increase ‘usual’ insulin by 10% if recent blood glucose is greater than 10mmol/L
  • Calculate STAT dose as 10 - 20% of your total daily dose of insulin
  • For example:
    • if total daily insulin dose is 40 units, 10 -20 % will be a dose of 4 - 8 units
  • Use short acting insulin for STAT dosing e.g. Actrapid/ Novorapid/ Humalog/ Apidra
  • Recheck blood glucose and ketones in 1-2 hours
  • Repeat STAT dose at intervals of 2-4 hours if needed
  • If in any doubt (or if unable to arrange recheck of blood glucose and ketones as above) please speak to DSN/Diabetes Team or Medical Registrar on call out of hours

Ketone Monitoring

In addition to monitoring blood glucose, you should check ketone levels when you are unwell, particularly if blood glucose is greater than 14mmol/l on 2 occasions.

If ketones are elevated (above 0.6mmol/L) and you have any of the following:

  • High Blood Glucose with excessive thirstiness/ passing urine
  • Dehydration
  • Vomiting or unable to tolerate oral fluid,
  • Abdominal pain
  • Breathlessness


  • You are Pregnant

then emergency admission to hospital is required to exclude diabetic ketoacidosis.


For advice on what to do when ketone levels are moderately raised but no severe symptoms, see the table below. You should always seek emergency advice if ketones are above 3.0mmol/L.


Urine Ketone

Blood Ketone



Less than 0.6 mmol/L

Within normal range however during illness test again 2-4 hourly


0.7 - 1.5 mmol/L

Give extra dose of insulin. Refer to sick day rules on previous page. Test blood glucose & ketones 1-2 hourly


1.6 - 3 mmol/L

Give extra dose of insulin. Refer to sick day rules on previous page. Seek advice from your diabetes team / Gp / NHS 24: 0845 4242 424. Retest blood glucose and ketones 1 - 2 hourly


More than 3 mmol/L

Give extra dose of insulin. Refer to sick day rules on previous page. Seek advice from your diabetes team / Gp / NHS 24: 0845 4242 424 or attend accident & emergency urgently

Blood ketone meter range 0.0 mmol/L–8.0 mmol/L

For more information on Interpretation of ketones during illness read the Ketones Page

For more information from trend UK, click here


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