Management of adults with type 2 diabetes who require bowel preparation

Patients with type 2 diabetes and multiple comorbidities should be admitted to hospital for the duration of the bowel preparation to have their blood glucose concentrations and fluid balance monitored.

Some antihyperglycaemic drugs have an increased risk of complications with bowel preparation and require specific management.

Sodium-glucose co-transporter 2 (SGLT2) inhibitors have been associated with the development of diabetic ketoacidosis (DKA). The risk and severity of SGLT2 inhibitor–associated DKA are increased during bowel preparation and the periprocedural period because of prolonged fasting, dehydration and decreased carbohydrate intake. Bowel preparation is usually started the day before a procedure. In patients undergoing surgery and procedures requiring bowel preparation (including colonoscopy), stop the SGLT2 inhibitor for at least 4 days—3 days before the procedure (which is usually 2 days before the bowel preparation) and the day of the procedure.

Any patient who has been taking an SGLT2 inhibitor who becomes unwell (ie has abdominal pain, nausea, vomiting, fatigue or metabolic acidosis) during bowel preparation, or in the week following a bowel procedure, should have their blood ketone concentration checked, even if their blood glucose concentrations are not elevated and the SGLT2 inhibitor was stopped before the bowel preparation. See SGLT2 inhibitors in Postprocedural management of adults with type 2 diabetes for information on restarting an SGLT2 inhibitor after the procedure.

For patients with diabetes and chronic kidney disease stage 3 or more (or creatinine clearance less than 40 mL/min), metformin should be stopped when the bowel preparation starts, because of the risk of dehydration and deteriorating kidney function. Metformin should not be restarted until kidney function returns to baseline and the patient is eating and drinking normally.

Sulfonylureas should be stopped when only clear fluids are allowed as part of the bowel preparation. This is to minimise the risk of hypoglycaemia occurring.

Patients with type 2 diabetes who are using insulin can be managed the same way as patients with type 1 diabetes, continuing basal insulin and omitting prandial (mealtime) bolus insulin doses; see Instructions for patients with type 1 diabetes having a bowel procedure.