Colonoscopy Perparation (Bowel preparation – Moviprep / Plenvu / Picolax) for People with Diabetes Controlled with Insulin (or Insulin and Tablets)
Please bring all your diabetes medications into hospital with you and your blood glucose testing kit (if you have one)
If you are driving, wait until your blood glucose level is above 5mmol/L on finger prick test
Please follow instructions in the table overleaf marked ‘What to do with your medication before procedure’
Please follow these instructions about eating and drinking for your bowel preparation. You may find that your glucose levels are different to normal. The food you are eating for your procedure has less fibre and is absorbed more readily. This can lead to blood glucose spikes and higher levels as the food is absorbed more quickly. This is followed by lower levels as the food is used up faster than normal.
If you have any concerns, contact your diabetes practice nurse or contact the diabetes nurses at Dorset County Hospital on 01305 255342.
If you have any symptoms of low blood sugar such as sweating, dizziness, blurred vision or shaking, please test your blood sugar with a finger prick test . If it is less than 4mmol/L, take 4 or 5 glucose tablets or 150ml of apple juice or non-diet lemonade or 100ml sugary drink (e.g. Lucozade® Energy Original). Re-test your blood sugar 10-15mins later. If blood sugar is still less than 4mmol/l, take another 4 glucose tablets or a sugary drink. Please tell staff at the hospital that you have done this. It is possible that, for your safety, your procedure may have to be postponed.
After the procedure
After the procedure your blood glucose will be checked and if necessary additional insulin given. When you have recovered, you will be offered food and drink. When you are eating and drinking normally, you should resume taking your normal insulin and/or tablets unless advised differently by nurses in the Endoscopy Department. Please note, your blood glucose levels may be a little unsettled for a day or so.
If you do not improve quickly or have any other concerns, please phone your GP practice for advice.
What to do with your medication prior to your procedure
| Medication | Day before the procedure | Day of procedure | |
| Morning appointment | Afternoon appointment | ||
| Once daily (evening) Lantus®/Glargine or Toujeo® Semglee® or Abasglar® Tresiba®/Degludec or Insulatard®or Humulin I® | Decrease dose by a fifth (20%) If you are unsure about working out this dose, please contact you diabetic nurse specialist / GP for advice | Take normal dose | Take normal dose |
| Once daily (morning ) Lantus®/Glargine or Toujeo® Semglee® or Abasaglar® Tresiba®/Degludec or Insulatard®or Humulin I® | Decrease dose by a fifth (20%) If you are unsure about working out this dose, please contact your diabetic nurse specialist / GP for advice | Reduce dose by a fifth (20%). Your blood glucose will be checked on admission | Reduce dose by a fifth (20%). Your blood glucose will be checked on admission |
| Twice daily Novomix 30®, Humulin M3®, Humalog Mix 25® | Take half usual dose | Take half usual dose then resume your normal insulin with your first meal after the procedure | Contact diabetes specialist team for advice on dosing |
| Basal Bolus (a long acting insulin in addition to a pre meal short acting insulin) Novorapid® or Fiasp® Humalog® or Lyumjev® Apidra® | Continue to take insulin before your meals You may need slightly less to avoid hypoglycaemia Omit short acting insulin once fasting begins | No breakfast so omit short acting insulin dose Resume your normal insulin once eating normally again Continue to take long-acting insulin – dose need to be reduced | Omit short acting insulin doses not eating Resume doses once eating normally again Continue to take long-acting insulin – dose may need to be reduced |
You should resume taking your normal insulin 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