Return To Services

Service Information

Managing your diabetes

Managing your diabetes when you are well and unwell

How to take a blood sample to check your HbA1c, and how to recalculate your insulin dose when you are unwell – the “sick day rules”.

How to collect a blood sample

Watch a video explaining how to collect a blood sample to test your HbA1c. The video opens in a new window which takes you to YouTube where accessibility controls may not be supported.

The “sick day rules” for people with type 1 diabetes

People with diabetes can develop an illness like anyone else.  However, illnesses can make blood glucose levels go up or down.  You should see your GP about the illness itself, but these guidelines may help with your diabetes management while you are ill:

  • Test blood glucose levels every 2 hours
  • Test for blood ketones
  • Drink plenty of fluids
  • Never stop taking insulin without discussion with the diabetes team

Some illnesses can cause high blood glucose levels even if you are not eating as much as normal.
This is because during illness the body starts to use other “fuels” such as fat, and also releases glucose that the body stores in the liver. Ketones are made when fat is used as an energy source in the body. Ketones can be detected in the blood and urine.

Production of ketones means the body is in trouble.

If ketones continue to be produced you are heading for Diabetic KetoAcidosis (DKA) and this must be taken seriously.

Illness also places a stress on the body and this can cause hormones to be released such as cortisol, that interferes with the action of insulin. This is why more insulin may be needed to keep the blood glucose levels under control.

Diarrhoea and vomiting

A diarrhoea and vomiting bug (gastroenteritis) sometimes means that blood glucose levels can drop. It is important to continue drinking to stop dehydration. If you are struggling to keep fluid down, try using a straw or suck an ice cube slowly.

Treat episodes of low blood glucose (less than 4 mmol/1) as you normally would, and think about a reduction of your insulin if the blood glucose level stays low. Remember to go back to the normal dose once your blood glucose level rises again.


Sometimes ketones will occur even if the blood glucose levels are low. These ketones are produced by the body going into ‘starvation mode’. Food as well as insulin is required to turn off ketone production.
The blood ketone meters can not tell the difference between ‘starvation’ ketones and the ones caused by a lack of insulin.

If you are unwell with ketones present and your blood glucose levels are high you may need extra fast-acting insulin.

The extra insulin required should be worked out according to how many ketones are present.

Step 1. Work out your usual Total Daily Dose (TDD) of insulin by adding together all of the insulin given in a 24 hour period.

Step 2. Work out 10% and 20% of your Total Daily Dose.

Step 3. Test the blood glucose and blood ketone level every 2 hours and give additional insulin:

  • Blood ketone level less than 0.6mmol/L (urine -trace).  Give the usual correction dose, every 4 hours
  • Blood ketone level 0.7 – 1.5mmol/L (urine – moderate). Give 10% instead of your usual correction dose, every 2 hours
  • Greater than 1.5mmol/L (urine – lqe). Give 20% instead of your usual correction dose, every 2 hours

Step 4. Give this fast-acting insulin as well as your usual insulin dose for food, until the blood glucose level is in single figures and the ketones are reducing.

Step 5. Contact a medical professional immediately if you have ketones AND you:

  • become drowsy
  • keep vomiting (more than 6 hours)
  • have severe abdominal pain
  • are dehydrated (dry lips, less urine, sunken eyes)
  • ketones present and no reduction after 2 correction doses


If your GP practice is closed please phone NHS Direct at 111 for more advice or come to your local emergency department. Inform them that you are worried about “Diabetic keto-acid-osis” as you will require admission to hospital for assessment.
Bring your capillary blood glucose and ketone meter and test strips with you, as well as your
insulin pens or needles.

Contact the Ipswich Hospital diabetes team in office hours

01473 704 180
Back to top Print This Page