If you have a colonoscopy coming up, you may be more worried about the prep than the procedure itself. That is normal. The good news is that the prep is temporary, predictable and very doable with a little planning. This guide walks you through it one day at a time.
Your instructions from our office come first. This article gives general tips. Your written instructions are made for you, your medicines and your health. If anything here differs from them, follow your instructions, and call the office at (424) 281-7392 if you are unsure.
Why does the prep matter so much?
During a colonoscopy, the doctor looks at the lining of your colon with a thin, flexible camera, looking for polyps (small growths) and other changes. If stool is left behind, it can hide polyps, and the exam may need to be repeated sooner. A clean colon means a more complete exam, and a better chance that your next one can wait years. In other words, a good prep is the part of the exam that you control.
One week before: plan ahead
A little planning now prevents last-minute stress.
- Read your instructions all the way through. Note the times you need to start the diet, take each dose and arrive.
- Review your medicines. Tell the office if you take blood thinners, insulin or other diabetes medicines, GLP-1 medicines (such as semaglutide or tirzepatide), or iron pills. Some may need to be adjusted or paused. Do not stop any medicine on your own unless your instructions say so.
- Arrange your ride. You will receive sedation, so you need an adult to take you home. More on this below.
- Pick up your prep. Fill the prescription or buy the products listed in your instructions, so you are not searching for them the day before.
- Plan your time off. Most people take the procedure day off, and some take the afternoon before off too.
Your shopping list
Having everything at home makes the day before much easier. A typical list:
- The bowel prep your instructions name, plus any tablets they list
- Clear liquids you like: clear broth or bouillon, apple juice, white grape juice, lemon-lime soda, ginger ale, sports drinks and electrolyte drinks
- Gelatin and ice pops in yellow, green or orange flavors (nothing red, blue or purple, because those colors can look like blood or hide the lining)
- Coffee or tea, to drink without milk or creamer
- Hard candy or lemon drops in light colors, to help with the taste
- Soft toilet paper or flushable wipes, and a barrier cream such as petroleum jelly or zinc oxide to protect your skin
- A straw, and a phone charger for the bathroom
Low-fiber foods for the days before, such as white bread, white rice, eggs, chicken, fish, plain pasta and yogurt, are also worth having on hand if your instructions call for a low-fiber diet.
Two to three days before: go low-fiber
Many prep instructions ask you to switch to a low-fiber diet for a few days before the procedure. Fiber is the part of plant foods your body does not fully digest, so it can stay in the colon and get in the way.
Low-fiber foods
White bread, white rice, plain pasta, eggs, tender chicken or fish, tofu, yogurt, cheese, and well-cooked vegetables without skins or seeds.
High-fiber foods
Nuts, seeds, popcorn, corn, beans, whole grains, brown rice, raw vegetables, salads, and fruit with skins or seeds.
If you eat a lot of beans, corn tortillas or fresh fruit day to day, as many families in Los Angeles do, this change can take some planning. Rice, eggs and soft chicken or fish make easy meals for these few days. Drink plenty of water too.
The day before: clear liquids and the first dose
This is the main prep day. Most people do best when they treat it as a stay-at-home day.
Clear liquids only
From the time your instructions say, have only clear liquids: things you can see through, with no pulp, milk or red or purple color. Drink often through the day. Staying well hydrated makes the prep work better and helps you feel less tired.
Start the first dose
Usually in the late afternoon or evening, you drink the first half of your prep over a set time. Bowel movements often start within one to three hours. Stay close to a bathroom.
Keep drinking
Follow each dose with the extra clear liquids your instructions list. This is an important part of the prep, not an optional extra.
Rest when you can
Go to bed early if the timing allows, and set an alarm for your second dose.
Tips for drinking the prep
- Chill it, unless your instructions say otherwise. Cold usually tastes better.
- Drink through a straw placed toward the back of your tongue.
- Take a sip of a clear drink or suck on a light-colored hard candy between glasses.
- If you feel sick to your stomach, take a 20 to 30 minute break, then continue more slowly.
- Walk around between glasses. Gentle movement can help with bloating.
- Use wipes and barrier cream early, before your skin gets sore.
The morning of your colonoscopy
Most instructions now use a split-dose prep: half the evening before, and half on the morning of the procedure. Splitting the prep this way usually cleans the colon better, and the American College of Gastroenterology and other national groups recommend it. You may need to wake up early, sometimes before dawn, to finish the second dose on time.
- Finish the second dose by the time your instructions give. After that, you will be told to stop eating and drinking for a period of time before sedation. This is for safety.
- Take only the morning medicines your instructions allow, with a small sip of water.
- Wear comfortable, loose clothes and leave jewelry and valuables at home.
- Bring your photo ID, insurance card, a list of your medicines, and your driver's name and phone number.
If you are also having an upper endoscopy (EGD) the same day, the prep is the same; the upper exam needs only the period of not eating and drinking.
What does a successful prep look like?
By the end of your prep, what comes out should be watery and clear or light yellow, a little like urine. It is fine if there are a few small flecks. Cloudy or brown liquid, or any solid stool, means the colon may not be clean yet.
Not clear by morning? Call the office for advice. Do not take extra laxatives on your own. It is much better to ask than to arrive with an incomplete prep.
Call the office if you vomit and cannot keep the prep down, if you have no bowel movements several hours after the first dose, or if you feel dizzy or lightheaded.
Call 911 or go to the nearest emergency room if you have severe or worsening abdominal pain, vomiting blood, black or bloody stools with dizziness or fainting, or you feel faint and cannot stay upright.
Getting there and getting home
Dr. Pimienta performs colonoscopy at Specialty Surgical Center of Beverly Hills, 8670 Wilshire Blvd, Suite 300, less than a mile west of his Wilshire office. Traffic on Wilshire Boulevard and the streets around Beverly Hills can be heavy and unpredictable, especially in the morning. Even a short drive can take much longer at rush hour or when there is an accident on the way.
- Leave extra time. Check traffic before you go, and aim to arrive at the time your instructions give, not later.
- Bring a responsible adult. Sedation affects your judgment and reflexes for the rest of the day, so you cannot drive, and you should not travel home alone on Metro, a bus or a rideshare. Many centers will not start sedation unless a friend or family member is there to take you home. Your instructions will say what the center requires.
- Plan the rest of the day. No driving, work, alcohol or important decisions until the next day. Most people feel ready for a normal meal within a few hours, unless they are told otherwise.
Before procedure day, you can reach the office for consultations by Metro: the Wilshire office is a few blocks west of the D Line Wilshire/Fairfax station. On procedure day, though, plan on a ride with someone you trust.
Afterward, some gas and bloating are common because air is used to open up the colon during the exam. Walking helps. If polyps were removed, you will be told when to expect results and when your next exam is due.
When to see a GI doctor
If you are 45 or older and have not been screened, have had a positive stool test, have a family history of colorectal cancer, or have symptoms such as rectal bleeding or a lasting change in bowel habits, it is time to talk with a gastroenterologist. Our colorectal cancer screening page explains your options, and our preparing for your procedure page covers the basics. Dr. Pimienta sees adults from across Los Angeles County, in English and Spanish. To get started, request an appointment and the team will call you back.