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HealthInfo Canterbury

Managing insulin when you are sick

If you are ill, need surgery, or go through a period of severe emotional stress, you may need to change your normal diabetes routine.

When you are unwell your body releases hormones that increase your blood glucose (sugar) levels. You may need more insulin, even though you may not be eating as much as usual, or even vomiting. This is why managing diabetes is different when you are sick, to stop you from developing high blood sugar levels.

If you have type 1 diabetes, you also need to avoid developing diabetic ketoacidosis (which is often called DKA).

If you are unwell:


See your doctor urgently if:

Guidelines for managing sick days

Surgery and fasting

FDP sick days surgeryIf you have to fast before having surgery or a medical procedure, make sure you have guidelines for adjusting your insulin beforehand. Speak to your GP about this.

Who to call

If you have questions, call your GP, practice nurse or an after-hours GP service.

Replacing fluid

You can take rehydration solutions, such as Gastrolyte, to replace fluid and electrolytes lost through diarrhoea or dehydration. However, rehydration solutions have relatively low concentrations of carbohydrates, so you may need extra carbohydrates.

Take care with sweetened fluids if you get diarrhoea. You may have to dilute them up to five times so you can absorb them well.

Written by nursing staff at the Diabetes Centre, Christchurch. Adapted by HealthInfo clinical advisers. Last reviewed July 2019.


See also:

Colonoscopy & sigmoidoscopy if you have diabetes

Images courtesy of David Castillo Dominici at

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Review key: HIDIA-21832