Gastroscopy / Flexible Sigmoidoscopy Preparation for People with Diabetes Controlled with Tablets or by Injections of GLP-1 Agonists
Bring all your diabetic medications into hospital. If you have a blood glucose testing kit, please bring it with you.
If you are driving, wait until your blood glucose level is above 5mmol/L.
Please follow instructions in the table overleaf marked ‘What to do with your medication before procedure’.
Preparing for appointments
- Do not drink fluids for four hours before the procedure
- Do not eat food for six hours before the procedure
- When you travel to and from hospital for your procedure, carry some glucose tablets or a sugary drink.
If you have any symptoms of low blood sugar such as sweating, dizziness, blurred vision or shaking, please test your blood sugar if you can do so. If it is less than 4mmol/L, take 4 or 5 glucose tablets or 150mls apple juice or sugary lemonade. Please tell staff at the hospital that you have done this. We might have to postpone your procedure.
After the procedure
After the procedure your blood glucose will be checked. When you have recovered, you will be offered food and drink. If you are eating and drinking normally later that day, restart your diabetes medications. Please note, your blood glucose levels may be a little unsettled for a day or so.
If you do not improve quickly or if you have any concerns, please phone your GP practice for advice.
What to do with your medication before the procedure
| Medication | Day before admission | Day of procedure | |
| Morning appointment | Afternoon appointment | ||
| Acarbose | Take as normal | Omit morning dose and resume when eating normally | Take your morning dose if eating breakfast. Do not take your lunchtime dose |
| Repaglinide or nateglinide | Take as normal | Omit morning dose and resume when eating normally | Take your morning dose if eating breakfast. Do not take your lunchtime dose |
| Metformin | Take as normal | Omit morning dose and resume when eating normally | If eating, take as usual with meals If not eating, omit dose |
| Sulphonylureas (e.g. glibenclamide, glipizide, gliclazide, glimepiride) | Take as normal | Omit morning dose and resume when eating normally | Take half the dose on the day of the procedure |
| Pioglitazone | Take as normal | Omit morning dose and resume when eating normally | If eating, take as usual with meals If not eating, omit dose |
| DDP-4 inhibitors (e.g. sitagliptin, saxagliptin, linagliptin) | Take as normal | Omit morning dose and resume when eating normally | If eating, take as usual with meals If not eating, omit dose |
| GLP-1 agonists (e.g Ozempic, Mounjaro, Semaglutide, Tirzepatide, Dulaglutide – Trulicity | Take as normal | Take as normal | Take as normal |
| SGLT-2 inhibitors (e.g. Dapagliflozin, Canagliflozin, Empagliflozin) | Take as normal | Omit morning dose and resume when eating normally | If eating, take as usual with meals If not eating, omit dose |
You should resume taking your normal tablets the morning after the procedure. However, your blood glucose may be higher than usual for a day or so.
About this leaflet
Author: Dinsdale Marjoram
Written: January 2026
Approved: March 2026
Review date: January 2029
Edition: v1