Navigating a Colonoscopy with Diabetes: Advice and Guidance
Specific dietary instructions and new medication schedules are common in the days leading up to a colonoscopy but can be especially challenging for people with diabetes. Here’s how to prepare for a colonoscopy with diabetes, plus how to manage your blood glucose levels before, during, and after the procedure.
Whether you’ve reached your 45th birthday or have had symptoms that might suggest colon or rectal problems, be prepared to have a healthcare professional order a colonoscopy.
A colonoscopy is the most reliable test to prevent and detect colon cancer – hopefully catching it in its earliest stages. A colonoscopy, usually performed in an outpatient facility, is done with a tiny camera to examine the colon (large intestine) and rectum via a long flexible tube known as a colonoscope.
The procedure is commonly done under anesthesia to minimize discomfort, while a healthcare professional guides the tube through the rectum and colon to look for growths called polyps. Polyps can be removed during the procedure and tested to see if they are benign, precancerous, or cancerous.
Why get a colonoscopy?
This test can help prevent you from developing cancer – which is particularly important for those with diabetes. A recent study found that people with type 2 diabetes had a 47% greater risk for colorectal cancer, compared to people without diabetes. In addition, a 2015 study found the risk of developing colorectal cancer increased among people with diabetes who also had obesity for four or more years.
Who should get a colonoscopy?
The Centers for Disease Control and Prevention (CDC) recommends adults between the ages of 45 and 75 get regular colonoscopies, and then as recommended by their healthcare professional for people over the age of 75.
Colonoscopies can be done earlier in life if you have a family history of colorectal cancer, or you experience symptoms such as stomach pain, ongoing constipation, diarrhea, or rectal bleeding. Your healthcare team may also suggest other tests for colorectal screening – learn more about these here.
If your healthcare professional wants you to schedule a colonoscopy, make sure you discuss the details surrounding diabetes management with them first, said Tami Ross, a spokesperson for the Association of Diabetes Care & Education Specialists (ADCES).
“Talk with your primary care provider and endocrinologist (if you have one) about the best plan for you to manage your blood glucose before, during, and after the test,” she said. “Any medical test that causes you to miss a meal or change your usual eating plan requires prior planning to keep your blood glucose from becoming too high or dropping too low.”
It’s important to follow all guidelines about what to eat a few days before the test, how to prepare your body for it, and how to fully recover from the procedure.
How to prepare for a colonoscopy
Be sure to speak with your healthcare team about what preparation for your colonoscopy will include.
“It is critical to achieve an adequate – and preferably an excellent – bowel preparation,” said Ala Sharara, a professor of medicine at the American University of Beirut and consulting professor at Duke University Medical Center.
If the colon is not fully cleared, the test is less likely to find any potential problems. It could also result in having to undergo the test a second time, which can be inconvenient and costly. Here are some tips on how to prepare for the procedure.
1. Mention diabetes upfront
“When you make your appointment for the colonoscopy, mention you have diabetes,” said Ross. “Ask for any specific instructions and have a list of all your medicines, doses, and when you take them.”
2. Choose a morning appointment
Opting for a morning appointment rather than an afternoon one minimizes the time spent fasting during the day so you can get back to your regular diet and medication regimen as soon as possible, said Ross.
An afternoon appointment means you’ll have to fast and manage your blood glucose levels for the entire day. However, going in the afternoon may be preferable for people who have to travel a long way to an endoscopy center.
3. Follow dietary instructions before the procedure
The healthcare professional who oversees your diabetes care will have specific instructions to help you before, during, and after the procedure. They may ask you to eat a specific diet a few days before the procedure and to drink a medicated liquid the day before the test, causing you to empty your bowels.
Some healthcare professionals may prefer that people eat a low-fiber diet for breakfast and lunch, followed by a clear fluid dinner, and then the bowel-emptying medication over two days. With this second method, people usually don’t go hungry or feel as nauseated, making the preparation more tolerable (and have less of an effect on blood sugar), said Sharara.
People who have chronic constipation may be advised to eat a low-fiber diet for two to three days or to take additional laxatives to fully empty the bowels.
4. Make adjustments as needed to your medication regimen
While preparing for a colonoscopy, it’s important that people with diabetes avoid hypoglycemia (low blood sugar), which means potentially altering your diabetes treatment before and after the procedure.
Because there are so many different combinations of diabetes medications, it’s difficult to provide broad guidance but here are some general guidelines:
- If you take oral medications, you may be told to pause them on the day of the exam.
- If you take metformin, your provider may tell you to stop taking it for two days before and two days after your colonoscopy.
- If you’re on short-acting insulin, you may be told to skip your insulin doses the day of the procedure (until you eat afterward).
- If you take long-acting (basal) insulin, you may be counseled on how to modify your insulin dose (sometimes by as much as half) before the test.
Do not stop or change any medications without recommendations from your provider first.
5. Keep a record of your blood sugar levels
Use a continuous glucose monitor (CGM) or blood glucose meter (BGM) to check your blood sugar levels while preparing for a colonoscopy. Check them before meals, at bedtime, the morning of the procedure (every few hours) and any time you feel you might be running high or low.
“Bring your blood glucose records from the previous 12-24 hours with you to the test, along with your diabetes supplies and hypoglycemia treatment,” said Ross.
If blood sugar is low (less than 70 mg/dL) while you are preparing for the colonoscopy or the day of the exam, take 15 grams of carbohydrates such as clear apple juice, white grape juice, or six ounces of regular sweetened clear or lemon-lime soda (as long as it’s done two or more hours before the appointment). If you prefer to use glucose tablets, talk to your healthcare professional to see if it’s okay to use three or four that aren’t red or purple, added Ross.
If you have type 1 diabetes and your glucose readings are above 240 mg/dL, it’s important to test for urine or blood ketones, said Ross. If ketones are present, contact your healthcare professional for further guidance.
What to expect the day of the test (and after it)
During the test, you will likely be put under anesthesia to minimize discomfort. As a result, you’ll likely be asked to come to the exam with a friend or family member who can drive you home. Plan to stay home the rest of the day after the procedure, though most people can usually be up and about after two to four hours.
“Take your diabetes medicine with you to the colonoscopy to take after the test as your healthcare professional suggests,” said Ross.
Do not take a double dose of the medications you missed. Your healthcare team may recommend checking your blood glucose more closely during the two to three days after your test to make sure things are back on track, she added.
“Remember that everyone is different,” said Ross. “Talk with your healthcare professional about the best plan for you, and get the instructions in writing so you don’t have to try to remember everything.”
Learn more about diabetes and digestive health here: