Management of adults with type 1 diabetes who require bowel preparation

Patients with unstable type 1 diabetes (eg frequent episodes of diabetic ketoacidosis, hypoglycaemic unawareness) or with multiple comorbidities should be admitted to hospital for the duration of the bowel preparation; an intravenous insulin infusion may be required.

Patients with type 1 diabetes must continue their basal insulin even while fasting, but dose adjustments may be needed when preparing for a bowel procedure; see Instructions for patients with type 1 diabetes having a bowel procedure. Patients with a planned colonoscopy or bowel surgery are usually required to drink only clear fluids for at least one day before the procedure. Glucose-containing clear fluids are recommended to provide some carbohydrate intake to avoid both hypoglycaemia and ketosis; clear fluids should not be ‘diet’ or ‘diabetic’ artificially sweetened drinks or jelly.

Note: While preparing for a bowel procedure, patients with type 1 diabetes should drink glucose-containing fluid to avoid hypoglycaemia and development of ketosis.

If possible, patients with type 1 diabetes should have their procedure scheduled for first on the morning list to minimise the time spent fasting.

Table 1. Instructions for patients with type 1 diabetes having a bowel procedure
The day before a bowel procedure On the day of the bowel procedure After the bowel procedure is completed
The day before a bowel procedure
On the day before a bowel diagnostic procedure or bowel surgery, patients can drink clear fluids throughout the day. Instruct patients to: continue basal insulin (either long-acting basal insulin injection or basal rate of rapid-acting insulin by CSII pump). Patients with a history of frequent episodes of hypoglycaemia or of hypoglycaemic unawareness should reduce the basal insulin to 80% of usual dose or rate (20% less than usual) omit usual prandial (mealtime) rapid- or short-acting bolus insulin doses to avoid hypoglycaemia measure BGC every 2 hours from waking until bedtime consider giving a supplemental (correction) dose of rapid- or short-acting insulin if BGC is more than 12 mmol/L. Wait at least 4 hours before giving a further supplemental dose to avoid insulin stacking and subsequent hypoglycaemia [NB1] drink glucose-containing clear fluids every 2 to 3 hours (eg glass of clear apple juice) to provide some carbohydrate intake treat hypoglycaemia with glucose-containing clear fluid, glucose gel or glucose tablets drink water, as well as glucose-containing clear fluids, to avoid dehydration.
On the day of the bowel procedure
Instruct patients or healthcare staff to: continue basal insulin: if subcutaneous basal insulin injection is normally given in the morning, give 80% of usual basal insulin dose (20% less than usual) if using a CSII pump, temporarily reduce basal insulin rate to 80% of usual rate (20% less than usual). Resume usual basal rate after the procedure when eating normally omit usual prandial (mealtime) rapid- or short-acting bolus insulin doses to avoid hypoglycaemia measure BGC hourly consider giving a supplemental (correction) dose of rapid- or short-acting insulin if BGC is more than 12 mmol/L. Wait at least 4 hours before giving a further supplemental dose to avoid insulin stacking and subsequent hypoglycaemia [NB1] treat hypoglycaemia, if fasting, with glucose-containing fluid, glucose gel or glucose tablet.
After the bowel procedure is completed
Instruct patients to: resume usual basal rate of CSII pump after completion of the procedure and when eating normally [NB2] give supplemental (correction) doses of rapid- or short-acting insulin if BGCs after the procedure are above the usual target. Wait at least 4 hours before repeating a supplemental dose to avoid insulin stacking and subsequent hypoglycaemia [NB1] restart usual prandial (mealtime) bolus insulin dose after the procedure when eating normally [NB2].
Note: BGC = blood glucose concentration; CSII = continuous subcutaneous insulin infusion NB1: See Supplemental (correction) insulin doses for information about calculating supplemental doses. NB2: If the patient has not resumed eating normally after the procedure, the insulin dose and regimen need review.