Preparing for your colonoscopy or upper endoscopy

Most people say the prep is the hardest part of a colonoscopy. It does not have to be stressful. With a little planning a week ahead, the right foods, and a few practical tips, most people get through it fine. This guide walks through the usual timeline, for patients across Los Angeles, before a colonoscopy or an upper endoscopy (EGD) at Specialty Surgical Center of Beverly Hills.

Why does the prep matter so much?

During a colonoscopy, Dr. Pimienta looks for polyps, some of them small and flat. Any stool left in the colon can hide them. A clean colon makes the exam more accurate, can make it shorter, and lowers the chance that you need to repeat it sooner. For an upper endoscopy, an empty stomach keeps you safe during sedation and gives a clear view.

What should I do, and when?

1. About 7 days before

   Read your instructions all the way through and get your prep from the pharmacy. Then review your medicines with our office, especially:

   • Blood thinners, such as warfarin, apixaban, rivaroxaban, dabigatran or clopidogrel
   • Diabetes medicines, including insulin, because you will be eating less
   • Iron pills, which can darken stool and make the colon harder to clean
   • GLP-1 medicines, such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound), which slow how fast the stomach empties

   Tell us about these medicines, and do not stop any of them on your own. Dr. Pimienta will tell you which to pause, which to adjust and which to keep taking. Also arrange a ride: an adult who can take you home after the procedure.

2. 3 to 5 days before

   Switch to lower-fiber foods, which leave less behind in the colon. Good choices include white bread, white rice, plain pasta, eggs, chicken, fish, tofu, yogurt, and well-cooked vegetables without skins. Avoid nuts, seeds, popcorn, corn, beans, whole grains, raw vegetables, and fruits with skins or seeds. Follow the number of days in your instructions.

3. The day before

   Drink only clear liquids all day, with no solid food. Drink plenty, not just water, so you stay hydrated and have some energy.

   In the evening, take the first half of your bowel prep. Most preps today are split-dose: half the evening before and half the morning of the procedure. Splitting the dose cleans the colon better and is easier to drink than all at once. Expect frequent, loose bowel movements starting within a few hours.

   Tips that help:

   • Chill the prep in the refrigerator, unless your instructions say otherwise.
   • Drink it through a straw placed toward the back of your tongue.
   • Chase each glass with a clear liquid you like.
   • Stay near a bathroom, and wear comfortable clothes.
   • Protect your skin: use soft toilet paper or flushable wipes, and a barrier cream or petroleum jelly.
   • If you feel sick to your stomach, take a short break of about 30 minutes, then keep going.

4. The day of

   Take the second half of your prep at the time in your instructions, usually several hours before your arrival time. That can mean setting an early alarm. Finish all of it.

   After that, stop all food and drink, including water, gum and candy, for the time your instructions give before the procedure. This "nothing by mouth" window is for your safety during sedation. If you were told to take certain medicines that morning, take them with a small sip of water.

   What to bring: a photo ID, your Medicare card if you have Medicare, your list of medicines, glasses or a case for contact lenses, and the name and phone number of your ride.

   What to wear: loose, comfortable clothes and flat shoes. Leave jewelry and valuables at home.

What counts as a clear liquid?

A clear liquid is one you can see through. It can have color, as long as it is not red or purple.

• Water, sparkling water and plain tea
• Black coffee, with no milk or creamer
• Clear broth or bouillon (chicken, beef or vegetable)
• Apple juice, white grape juice and lemonade without pulp
• Clear sports drinks and clear sodas, such as ginger ale or lemon-lime soda
• Gelatin and ice pops without fruit pieces or cream

How do I know my prep is working?

By the end, what comes out should be clear or yellow liquid, like urine or weak tea, with no solid pieces. A little cloudiness or a few flecks are usually fine. If you are still passing brown or solid stool after finishing the prep, or you could not finish it, call our office. Do not skip the second dose because your stool already looks clear; the second dose finishes cleaning the whole colon, including the far end where it meets the small intestine.

If you have not had any bowel movement within a few hours of starting the prep, or you have bad belly pain or keep vomiting, call us.

What if I am only having an upper endoscopy?

The prep for an EGD alone is simpler. You do not need a bowel prep or a low-fiber diet. In general, you will have nothing to eat for several hours before the exam (often from the night before), and clear liquids only until a set time, then nothing by mouth. The medicine review still matters, especially for blood thinners, diabetes medicines and GLP-1 medicines. You still need a ride home. If you are having an EGD and a colonoscopy the same day, follow the full colonoscopy prep.

What happens after my procedure?

You go home the same day with your ride. Gas and bloating are common for a few hours after a colonoscopy, and a mild sore throat is common after an EGD. Most people can eat a light meal soon after and are back to normal the next day. Drink plenty of fluids to replace what the prep took out. Do not drive, work or drink alcohol for the rest of the day. Dr. Pimienta goes over what he found and when you will hear about any biopsy results.

For more practical tips, read our article a practical guide to colonoscopy prep. If you are a new patient, the new patients page explains the portal and forms.

Questions patients ask

References

1. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Colonoscopy.
2. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Upper GI Endoscopy.
3. MedlinePlus (US National Library of Medicine). Clear liquid diet.
4. American Cancer Society. Colonoscopy.