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HealthInfo Waitaha Canterbury

Diabetes & endoscopy

Whakamātaunga kōpiro me kōpiro o raro me he matu huka tōu

FDP blood sugarThis information is to help you manage your diabetes before your procedure. Read it with the pamphlet that you've received from the Gastroenterology Department about preparing your bowel for your colonoscopy, sigmoidoscopy or capsule endoscopy.

The advice on this page will be enough to help most people manage their diabetes before their procedure. But if you've recently been admitted to hospital because your diabetes is poorly controlled, or if you're having major problems with low blood glucose (hypoglycaemia), make sure you talk to your general practice team.

Some people may need to go to hospital to prepare for their colonoscopy, sigmoidoscopy or capsule endoscopy.

Managing your diabetes will probably be easier if you have a morning appointment. If you do not have a morning appointment, phone the number on your booking letter to see if your procedure can be rescheduled to an earlier time.

Carefully read the information about food and clear fluids on the pamphlet you've been given on bowel preparation.

Do not worry if your blood glucose level is not as well controlled as usual as long as it's above 4mmol/L and below 15mmol/L.

Bring your blood glucose monitor, insulin and injecting equipment with you to the appointment. Also bring some dextrose tablets or whatever you would normally use to manage hypoglycaemia.

Getting prepared

If you take tablets for diabetes

If you're using insulin

Depending on how much carbohydrate you manage to take when you're just on fluids and what your blood glucose levels are, you'll need less insulin than usual. It's important to monitor your blood glucose levels at least four times a day and more often if you have any symptoms of hypoglycaemia. See the information below on what clear fluids you can use to raise your glucose level if it's too low.

If you're having an injection of long-acting insulin in the morning (Lantus, Protaphane, Humulin NPH)

If you're having an injection of long-acting insulin in the evening (Lantus, Protaphane, Humulin NPH)

If you're having one or more injections of mealtime insulin (NovoRapid, Apidra, Humalog, Actrapid, Humulin R)

The amount of mealtime insulin you'll need depends on how much carbohydrate you get from the clear fluids.

If you're having two injections a day of pre-mixed insulin (NovoMix 30, Humalog Mix 25, Penmix 30, Humulin 30/70, Penmix 50, Humalog Mix 50)

Taking carbohydrates in clear fluids

FDP bubbles in glassThese clear fluids have a similar amount of carbohydrate to one medium slice of bread (15 g of carbohydrate):

You'll digest carbohydrates in clear fluids more quickly than other carbohydrates, so be sure to spread the fluids through the day. Have some of the fluids listed above as well as the other clear fluids mentioned in your pamphlet at lunchtime, some mid-afternoon, some at dinnertime, some after dinner and some at midnight, depending on your blood glucose readings.

You can also have some of these carbohydrate-containing fluids up to the time specified on your procedure information pamphlet. If you needed any after that time because your blood glucose was low, let the staff know when you arrive for your procedure.

Written by Endocrinology and Diabetes Services, Christchurch Hospital. Adapted by HealthInfo clinical advisers. Last reviewed November 2022.


See also:

Managing insulin when you are sick

Page reference: 96281

Review key: HIDIE-96281