With Diabetes

Instructions for the Patient with Diabetes undergoing Colonoscopy

These are general guidelines. Please call the health care provider who manages your diabetes if you have additional questions.

For people with diabetes, any medical test that causes you to miss a meal or change your usual meal plan will require planning to keep your blood sugar numbers from becoming too high or low.

  1. Test blood sugar before meals, and bedtime, on preparation day and morning of the colonoscopy test. Test your blood sugar if you are feeling that you might be too high or low. If you are unaware of your low sugar feelings, test every two to three hours. Blood sugar may not return to your usual numbers for up to 72 hours after the colonoscopy.
  2. If you have a low blood sugar on preparation and/or test day, you must treat it with one of the following: four or five glucose tablets non-red or purple in color, ½ cup apple juice, ½ cup white grape juice, or 1 cup real soda (15 grams of carbohydrate) and test your blood sugar more times than usual during the day while trying to keep blood sugar numbers between 100 and 200mg/dl. If low blood sugar persists, contact your health provider for guidance.
  3. Bring the last 12 hours of your blood sugar record with you to your colonoscopy test. Bring your diabetes supplies, such as glucose tablets or other sugar source, with you to the colonoscopy test. Be sure to tell the staff if you are experiencing a low blood sugar feeling.
  4. During preparation day (day before the test), drink both sugar free and sugar containing drinks (see second page for options and menus).
  5. On test day you may have carbohydrate containing clear liquids (see Page 2) until 2 hours before the scheduled test time. If you have a low sugar during nothing by mouth time, use glucose tablets.
  6. Replace usual meals with 45-60 grams of liquid carbohydrate or 1 ½ cups to 2 cups. Liquid carbohydrate is absorbed in the stomach more rapidly and could increase the chance of low blood sugar. Follow insulin dosing for carbohydrate liquid meals as recommended by your provider.

Examples of sugar containing clear liquids (or 15 grams of carbohydrate) to be used for meals or a snack:

  • apple or white grape juice ½ cup = 15 grams
  • jello (non-diet) ½ cup = 20 grams
  • popsicles ½ cup = 15 grams
  • regular soda ½ cup = 15 grams
  • Gatorade® 1 cup = 15 grams
  • kool-aid ½ cup = 10 grams
  • Clear Boost® ½ cup = 18 grams or Clear Ensure® ½ cup = 16 grams

On the test day (until two hours before the test time), mix clear liquids with an equal amount of water.  Then do not eat or drink anything until after the test. 

Clear liquid food items that are sugar free:

  • fat-free broth, bouillon, or consommé
  • diet clear soda
  • coffee or tea, unsweetened or diet
  • seltzer and flavored water
  • Resource® Breeze-10 gram protein drink




Apple or white grape juice (1 cup)

Consommé or Broth (3/4 cup)

Consommé or Broth (3/4 cup)

Regular sweetened gelatin (1 cup)

2 orange popsicles (1 cup)

Clear juice (1 cup)

Resource® Breeze (1 cup)

Italian Ice (1/2 Cup)

Regular gelatin (1 cup)

Tea with Lemon (1/2 cup)

Regular gelatin (1/2 cup)

Tea with lemon (1/2 cup)

  1. If you have type 1 diabetes, you should check your urine for ketones if your blood sugar values are greater than 240mg/dl during preparation and test day. If ketones are moderate or large, contact your health care provider for further guidance.
  2. If you have any complications of diabetes, such as eye, foot or kidney problems, make sure you tell the staff during the check in process.
  3. If you have high or low blood sugar outside of suggested range of 100-200mg/dl and you cannot correct this, or have medication dosing questions, call your health care provider for help. If you have colonoscopy bowel preparation questions call UVA Endoscopy telephone (434) 982-0225.
  4. Restart your home medication schedule when the colonoscopy is over and you are eating a regular diet. Do not take extra dose of medicines to make up for missed dose amounts.
  5. If your diabetes medications change after receiving these instructions, please call the health care provider who ordered your colonoscopy test.