Diabetes and colonoscopy

The following are guidelines only – more specific questions can be handled by your health care provider.

**Note: If you have Type 1 Diabetes, please discuss with your Endocrinologist and do not follow the following instructions.

When you have diabetes, anything that causes you to change your usual meal routine requires special planning to safely manage blood glucose levels. Therefore, doctors will ask you to change your diet, insulin, and diabetes medication schedule to prevent low or very high blood glucose levels in preparation for the procedure.

Ask to schedule the colonoscopy early in the day so that you can eat afterwards and take your medication as close to the usual time as possible.

Insulin and Diabetes Pills
Download the PDF for information on diabetes medications and insulin (pages 2 and 3).

Blood Glucose Measurement
  1. Check your blood glucose levels before all meals, before bedtime the day before the procedure, on the morning of the procedure, and every 4 hours starting at 7:00 am the day of the procedure.
  2. Check your blood glucose level if you have any concerns or if you have symptoms of low or very high blood glucose levels.
  • If blood glucose level drops below 5 mmol/L, consume high glucose fluids.
  • If blood glucose level rises above 10 mmol/L, consume only glucose-free fluids.
  1. It is recommended to continue monitoring blood glucose levels in the few days following the procedure.
  2. Bring your blood glucose meter, test strips, a low blood glucose treatment and a snack with you on the day of the colonoscopy. Do not have any solid food before the colonoscopy and stop all liquids two hours before the colonoscopy.

Clear Fluid Diet

Many doctors will ask you to follow a clear fluid diet the day before the procedure.

Choose fluids that are high in glucose to maintain normal glucose levels.

  • Aim for 3 starch choices or 45 grams of glucose at meals.
  • Aim for 1-2 starch choices or 15-30 grams of glucose for snacks.
  • Avoid foods that are red or have red dyes (cherry, berry, or grape flavors) in the jell-O, popsicles, or juices.
Sample of Food Items with Glucose
Food choice (Portion / Grams of Glucose)
  • Apple juice/White grape juice (1/2 cup / 15 grams)
  • Jello (1/2 cup / 15 grams)
  • Popsicles (1/2 cup / 15 grams)
  • Kool-Aid (1/2 cup / 10 grams)
  • Regular soda (1 can / 40 grams)
  • Gatorade (1 cup / 15 grams)
  • Clear Boost (1/2 cup / 18 grams)
  • Clear Ensure (1/2 cup / 16 grams)
Sample of Food Items without Glucose
To prevent dehydration drink at least 2 liters of glucose-free clear fluids on your preparation day.
  • Fat-free broth (vegetables, beef, chicken)
  • Bouillon, or consommé
  • Sugar-free jello
  • Sugar-free pop
  • Flavoured water
  • Tea or coffee (no milk or cream)
  • Diet clear soda
  • Seltzer
Sample Menu
Breakfast (3)
  • Apple/grape juice (½ cup) and
  • Regular sweetened gelatin (1/2 cup) and
  • Tea with lemon
Lunch (3)
  • Consommé (1 cup) and
  • Regular sweetened gelatin (1/2 cup) and
  • Lemon-lime beverage
Dinner (3)
  • Consommé (1 cup) and
  • Regular sweetened gelatin (2 cups) and
  • Diet lemon-lime beverage