Diabetes: How to Prepare for a Colonoscopy
What is a colonoscopy?
A colonoscopy is a test that lets a doctor look inside your colon. The doctor uses a thin, lighted tube called a colonoscope to look for small growths (called polyps), cancer, and other problems like bleeding.
During the test, the doctor can take samples of tissue that can be checked for cancer or other problems. This is called a biopsy. A colonoscopy also lets the doctor take out polyps.
Before the test, you will need to stop eating solid foods. You also will drink a liquid or take a tablet that cleans out your colon. This will help your doctor to be able to see inside your colon during the test.
Before you schedule
When you make your appointment for the colonoscopy, mention that you have diabetes. Ask for any special instructions. Request an early morning appointment so you can get back as soon as possible to your normal routine for eating and taking medicines.
The doctor doing your colonoscopy (gastroenterologist) will want to know about all the medicines you take. Be sure to also tell him or her about any vitamins, supplements, and herbal remedies you take. It’s a good idea to have a list of all your medicines when you make your appointment.
If you take aspirin or some other blood thinner, your doctor will tell you if and when you should stop taking this medicine before your test.
Before the procedure
Talk with your diabetes doctor about how best to manage your blood sugar before and after the test.
Arrange to stay home on the day of the test. When you use the liquid or pills to clean out your colon, you will go to the bathroom a lot. You’ll get detailed instructions from the doctor on how to use the medicines (colon prep).
Discuss with your doctor the different types of medicines. You may need a type that is safest for people with kidney problems.
Stop drinking alcohol at least 1 day before and 1 day after your procedure. Alcohol could cause a strong reaction with the anesthesia medicines used during the test.
Managing blood sugar and medicines
Your doctor may have you track your blood sugar for at least 24 hours before and 72 hours after your test.
Plan on bringing your blood sugar meter and test strips with you to the test. Also, have glucose tablets or other quick sugar food with you in case your blood sugar drops too low.
If you take insulin or other medicine for diabetes, your doctor will give you exact instructions about how to take your medicines. You may need to change your diabetes treatment before and after the procedure.
Everyone is different. It’s important to talk with your doctor if you don’t understand what to do with your medicines. Get the instructions in writing, and bring them with you to the test.
Generally, if you take:
- Metformin, your doctor may have you stop taking it 48 hours before and after your colonoscopy.
- Diabetes medicine other than insulin, your doctor may have you stop taking your medicine on the morning of the test.
- Short-acting insulin, your doctor may have you stop taking it on the morning of the test.
- Long-acting insulin, your doctor may have you take only half of your usual dose on the morning of the test.
Bring your diabetes medicine with you to take after the test as your doctor suggests. Don’t take a double dose of medicines you’ve missed.
How to eat and drink
You’ll get detailed instructions about food and drink when you get the medicines to cleanse your colon. Generally, the day before the test, you’ll only be able to have clear liquids. These include water, tea, coffee, clear juices and broths, gelatin, and sports drinks.
Work with your diabetes doctor on how best to manage carbohydrate as you prepare for the test. You may want to plan 45 grams of carbohydrate for liquid “meals” and 15 to 30 grams for snacks. Apple or white grape juice and sweetened gelatins are a few options.
Tips for Colonoscopy Prep for Diabetics
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There are over 29 million diabetics in the United States, and the number is steadily increasing. Every year, thousands of diabetics schedule colonoscopies. If you have diabetes, a colonoscopy prep can be challenging because it means missing meals or changing your eating schedule. Therefore, it is especially important to monitor your blood sugar throughout the prep period.
Here are some tips for a successful prep that is compatible with a diabetic menu:
On the day before your colonoscopy, you should aim for 45 grams of carbohydrates at meals and 15 to 30 grams of carbohydrates for snacks. You have several options for clear liquids that have no carbohydrates. Some of these choices include fat-free broth or bullion, clear diet soda, coffee, tea (unsweetened or diet), seltzer and flavored water.
You can have clear liquids that do contain carbohydrates but you need to monitor the amount. Use this as a guide:
- 4 oz. apple juice— 15 grams
- 4 oz. white grape juice— 15 grams
- 8 oz. Gatorade— 14 grams
- ½ cup Jell-O (regular, sweetened)—15 grams
- Orange popsicle (read the label)—15 grams
- Italian ice (read the label)— 30 grams
- 1 teaspoon sugar (for coffee or tea)— 4 grams
Here is a sample menu for your prep day
|Apple or white grape juice— 1 cup||
Broth— ¾ cup
|Broth— ¾ cup|
|Regular sweetened gelatin— 1 cup||Italian ice— ½ cup||Strained fruit juice— 1 cup|
|Tea with lemon||Regular sweetened gelatin— ½ cup||Regular sweetened gelatin— ½ cup|
|Tea with lemon||Tea with lemon|
On the day of the colonoscopy
- Bring your glucose meter, test strips and low blood glucose treatment with you on the day of your procedure.
- Schedule the appointment for early in the day so that you can eat as soon as possible and take your medication.
- Resume your normal medication schedule.
New Study: Effective Colon Cancer Screenings Rely On Proper Bowel Prep
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Clear Liquids Diet
Need for the diet:
The clear liquid diet is a temporary diet that is used in several different settings:
- If you experience abdominal discomfort, such as cramps or pain, contact your doctor or nurse as soon as possible.
- The clear liquids diet does not provide enough energy, protein and many other nutrients for daily use. This diet is temporary and should not be used for more than 5 days. If you are on this diet for more than 5 days, your doctor and/or dietitian will tell you which supplement to use.
- The amount of liquid that you drink or eat on this diet may be important. If your doctor sets a limit about the amount, follow those directions carefully.
How to choose the clear liquid diet:
Liquids that you can see through at room temperature (about 78-72 degrees Fahrenheit) are considered clear liquids. This includes clear juices, broths, hard candy, ices and gelatin. The table below will help you with your choices.
Clear Liquids Diet Options
|Choose these foods/beverages||Do not eat these foods/beverages|
|Fruits/Juices||Clear fruit juices without pulp such as apple juice, grape juice, cranberry juice.||Nectars, canned, fresh, or frozen fruits.|
|Soups||Broth, bouillon, fat-free consommé.||Cream soups, soups with vegetables, noodles, rice, meat or other chunks of food in them.|
|Beverages||Coffee, tea (hot or cold), Kool-Aid, soda, water, lactose-free supplements if recommended by your doctor.||All others.|
|Sweets and Desserts||Fruit ices (without chunks of fruit), plain gelatin, clear hard candy, popsicle made from clear juices.||All others.|
|Milk and Dairy Products||None||All|
|Bread, Cereals and Grain Products||None||All|
|Meat, Chicken, Fish, and Meat Substitutes (nuts, tofu, etc.)||None||All|
|Oils, Butter, Margarine||None||All|
Sample Menu: Clear Liquids Diet*
*This diet contains approximately 1000 calories, 1 g fat and 14 grams of protein.
Credits for this dietary information go to Maureen Murtaugh, PhD.
Staying Safe Before a Medical Test
Q1. I have type 2 diabetes, and I’m having a colonoscopy soon. To prepare for this test, I can’t eat solid food but can only drink clear liquids the day before. I am afraid I’ll get hypoglycemic, as I often do when I don’t stick with my meal and snack schedule. Do you have any suggestions?
Great question! Fasting before any kind of test will affect your blood glucose level. In the hours before the test, be more vigilant than usual to make sure that you maintain a relatively normal glucose level. This means checking your blood sugar levels more frequently. On the night before the test, check your levels before dinner and again before bedtime. On the day of the test, check every one to two hours. Also, it’s important to talk to your doctor because it’s crucial that you have the procedure first thing in the morning. You should stress that you need to be the first patient the doctor sees that morning.
Also, here is some general advice about your medicines:
- If you take only oral medicines, you should not take them beforehand on the day of the procedure. If the procedure ends before noon, you may take your missed medicines at that time. If it ends later in the day, you should skip the morning dosage altogether and resume your regular evening dosage.
- If you are taking short-acting insulin, skip it until you’ve had a meal, and then take your regular dose.
- If you use a long-acting insulin, such as insulin glargine (Lantus), take half your usual dose the night before.
- If you have two intermediate-acting doses, take half your evening dose the night before the procedure and half your morning dose the day of the procedure. Resume your usual evening dose after the procedure.
Because you’re permitted to drink clear liquids the day before the procedure, you can have chicken or beef broth, clear carbonated beverages (not cola), Jell-O (not red or purple), or white grape and apple juices. I recommend that you drink these liquids every three hours or so throughout the day, up to midnight. This should prevent episodes of hypoglycemia, or low blood sugar. You must continue to check your blood glucose levels throughout the day as well. This is especially critical if you do not normally experience the warning symptoms that usually accompany low glucose levels, including tremors, sweating, nervousness, and dizziness.
Q2. I often forget to monitor my blood sugar and take my metformin. Is this dangerous? What are the possible consequences? I feel pretty good despite this.
— Pat, Illinois
Yes, forgetting to take metformin can be detrimental to your health. As a type 2 diabetic, you have insulin resistance and most likely some insulin deficiency. This limits your body’s capacity to metabolize glucose from your meals. If your body does not metabolize glucose well enough, then you will have a high glucose level, which is toxic to many organs in the body. Since diabetes is an everyday condition, on the days that you skip your medicines, your glucose levels will be high. This affects small blood vessels that provide nutrients and oxygen to the eyes, kidneys, heart, nerves, and brain. Unfortunately, you are not going to feel much in the early stages of the detrimental changes. In fact, in most cases, you develop symptoms only when the damage is irreversible. Simply having high sugar levels also may not produce any symptoms until the level exceeds the threshold of your kidneys’ capacity to excrete the excess sugar normally — usually above 200-250 mg/dl. This is not a safe level for many organ systems.
I recommend that you check your sugar levels at least twice daily. This will let you know the extent to which your sugar rises. It will also help you and your doctor determine the amount of medicine that your body requires. If you have difficulty taking medicines and you currently require a small dose of metformin, perhaps you can concentrate on diet and exercise to achieve good glucose control.
Learn more in the Everyday Health Type 2 Diabetes Center.