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Patient Instructions · United Gastroenterology Associates
CoLyte, TriLyte and GoLytely Prep Instructions
For colonoscopy patients at United Gastroenterology Associates in Cypress and Katy, CoLyte, TriLyte and GoLytely are 4-liter polyethylene glycol (PEG-3350) and electrolyte bowel preps taken as a split dose: about 3 liters the evening before your colonoscopy and the last liter 4 hours before you leave home on the day of your procedure. Follow the practice’s step-by-step instructions below, read the General Colonoscopy Instructions first, and call (346) 340-4414 with any questions. These instructions are for patients scheduled with Muhammad Ali Khan, MD, FACP, FASGE, at United Gastroenterology Associates.
Medically reviewed by Muhammad Ali Khan, MD, FACP, FASGE · Updated
Prep questions: (346) 340-4414
CoLyte Prep at a Glance
If Dr. Khan has prescribed CoLyte, mix the prep the morning before your procedure, shake until the powder dissolves and chill it in the refrigerator. Between 3 and 6 PM, start drinking an 8-ounce glass every 10 to 15 minutes until you have finished 3 liters (the container is three-quarters empty), then refrigerate the rest. Four hours before you leave home, drink the remaining liter at the same pace; it must be finished at least 3 hours before your arrival time. Stop everything by mouth 3 hours before your arrival time.
Important
Follow the instructions given to you by your doctor. Do not stop, start or change any medicine unless Dr. Khan's office or your prescribing doctor tells you to. If the instructions you received differ from this page, follow the instructions you received.
Have DIABETES? Read this first!
CoLyte and TriLyte and GoLytely Prep
IMPORTANT GLP-1 DRUG INFO
The following weight loss / diabetic drugs should be held as instructed prior to procedure:
- Liraglutide: Victoza (weekly) and Saxenda (daily)
- Dulaglutide: Trulicity (weekly)
- Exenatide: Bydureon (weekly) and Byetta (daily)
- Semaglutide: Ozempic (weekly), Wegovy (weekly) and Rybelsus (daily)
- Tirzepatide: Mounjaro (weekly) and Zepbound (weekly)
- Lixisenatide: Adlyxin (daily)
The medication will need to be stopped seven (7) days prior to your procedure if you are on a weekly dose or the day of your procedure if you are on a daily dose.
5-7 Days before your procedure
Have your prescription filled. Follow the prep instructions below. Questions about the procedure itself? See our colonoscopy services overview, or call the Katy office or Cypress office.
5 Days before your procedure
If you routinely have less than 2 bowel movements per week then you will also need to purchase an 8.3 oz bottle of Miralax. Begin taking a dose of Miralax twice a day 5 days prior to your procedure. Take the last dose of Miralax in the morning the day before your procedure.
3 Days before your procedure
AVOID raw fruits and vegetables, whole wheat/multigrain products, beans, nuts, popcorn and seeds.
1 Day before your procedure
You may only have clear liquids the entire day such as water, coffee, tea, broth, sodas, apple juice, Gatorade, Kool-aid, Jell-O, popsicles and hard candy. You may not have any solid food. It is important to drink extra clear liquids before your prep to maintain adequate hydration. Do not drink liquids that are not clear such as milk. Do not drink liquids that are red or purple in color.
1 day before your procedure
-
MORNING:
• Mix the prep according to instructions. Shake until the powder is mixed and chill in the refrigerator. BETWEEN 3 AND 6 PM – START YOUR PREP:
• Shake the container. Begin drinking the solution. Drink an 8 ounce glass of the solution every 10 – 15 minutes. It is recommended that you drink the whole glass rapidly rather than sip small amounts. A straw may help.
• Keep drinking the solution every 10-15 minutes until you drink 3 liters (bottle is 3/4 empty). Shake the container before pouring each dose. Refrigerate the unused portion.
• Make a conscious effort to drink as much clear liquids as you can before, during and after the preparation. NOTE:
• If you experience nausea – slow down your prep intake and walk around until nausea is relieved.
• Use baby wipes and/or Balneol cleansing cream or lotion during the prep to reduce irritation.
The day of the procedure – 4 HOURS before you leave home for your appointment
-
STEP 1:
• Begin drinking the remainder of the solution (1 liter). Drink an 8 oz. glass of the solution every 10 -15 minutes as directed above. Do not rush. If you need to wait longer between glasses, do so.
• Keep drinking the solution until the bottle is empty. This solution must be completed at least 3 hours prior to your appointment arrival time. STEP 2:
• You may drink clear liquids until 3 hours before your appointment time.
• You may take your prescription medications (except those listed in the booklet) with water up to 3 hours before your appointment arrival time.
• Do not use smokeless tobacco on the day of your procedure.
• Starting 3 hours before your appointment arrival time absolutely nothing by mouth including gum, hard candy, breath mints.
Please call us at (346) 340 4414 if you have any questions or if you are having difficulty with the preparation. We are available 24 hours a day, 7 days a week.
Make An AppointmentDiabetic Prep
Medications
- If you take oral medications for your diabetes, do NOT take your diabetes pills on the day prior to your procedure (prep day) or on the day of your procedure (until your procedure is complete and you resume a normal diet).
- If you take non-insulin injectable medications (Byetta, Bydureon, Victoza, Trulicity, Tanzeum, Symlin), do not take the medication if your injection day is the day prior to your procedure (prep day). You can resume it after the procedure is complete.
- If you take insulin, reduce your dose by 50% (half) of your normal dose on the day prior to your procedure and the day of your procedure. You can resume your normal dose after the procedure when you resume normal diet.
- If you use an insulin pump, contact your diabetes doctor for instruction. Generally, most patients will need to reduce their basal rate to 80% of the normal rate.
Diet
- You should aim for 45-60 grams of carbs with each meal. Although you may ordinarily avoid sugars, they are ok to take when you are prepping for your colonoscopy as these will be the main source of calories when you are on a clear liquid diet.
- For snacks, try to include other fluids that contain electrolytes such as broth.
- Examples of clear liquids with carb amounts are listed below. Note, if you experience low blood sugar (<60) during the 2 hours before your procedure, you can take 3 teaspoons of soda or clear juice to raise your sugar. Do NOT take solid foods or non-clear liquids, as your procedure will be cancelled.
FLUID
AMOUNT
CARBS
Juice
1/2 cup
15 g
Jello
1/2 cup
15 g
Soda
1 can
40 g
Popsicle
1 double stick
15 g
Gatorade/Powerade
1/2 cup
15 g
Broth (veg/chicken/beef)
any
0 g
Clear Protein Drinks
Clear Protein Drinks
0 g
Please call us at (346) 340 4414 if you have any questions or if you are having difficulty with the preparation. We are available 24 hours a day, 7 days a week.
Make An AppointmentKey Rules From the General Colonoscopy Instructions
These points summarize the general colonoscopy instructions from Dr. Khan's office. Read the full general colonoscopy instructions for details, and follow any personal instructions the office gives you.
- Driver: an adult must drive you home and stay at the center during your procedure.
- Blood thinners: ask the office for guidance before your procedure. Do not stop them on your own.
- GLP-1 medicines: tell the office if you take one. The instructions give separate timing for weekly and daily GLP-1 medicines.
- Iron, diet pills and herbal medicines: the instructions ask you to stop these 7 days before.
- Alcohol: avoid for 24 hours before and after your colonoscopy.
- Before arrival: nothing by mouth starting 3 hours before you arrive, except approved medicines with up to 2 tablespoons of water.
- Rescheduling: call at least 3 to 4 days ahead.
Tell the office before your prep if you
- Take a blood thinner or aspirin
- Have diabetes or take insulin
- Take a GLP-1 medicine
- Have kidney or heart disease
- Are pregnant or may be pregnant
These conditions can change how you prepare. The office will give you personal instructions.
Questions About Your CoLyte Prep?
If you are unsure about your prep, your medicines or your arrival time, call the office before you start.
If Your CoLyte Prep Is Not Working
Most preps start working within one to three hours of the first dose. If nothing has happened several hours after your first dose, if you are vomiting and cannot continue, or if your stool is still brown after the second dose, call (346) 340-4414 before your procedure. Read what to do if your colonoscopy prep is not working, what you can eat before a colonoscopy and low-residue foods before a colonoscopy. For the procedure itself, see colonoscopy services in Katy and Cypress.
CoLyte Prep FAQs
Answers to common questions from patients preparing for a colonoscopy with CoLyte, TriLyte and GoLytely.
What are CoLyte, TriLyte and GoLytely?
CoLyte, TriLyte and GoLytely are prescription bowel preps made of polyethylene glycol 3350 (PEG-3350) and electrolytes. The powder is mixed with water in a 4-liter container, and the solution flushes the colon so Dr. Khan can see the lining clearly during your colonoscopy.
When do I drink each part of the prep?
Start drinking between 3 and 6 PM the day before your procedure, one 8-ounce glass every 10 to 15 minutes, until you have finished 3 liters. Four hours before you leave home, drink the remaining liter the same way. The solution must be finished at least 3 hours before your appointment arrival time.
Should the prep be refrigerated?
Yes. Mix the prep the morning before your procedure and chill it in the refrigerator. Shake the container before pouring each glass and keep the unused portion refrigerated overnight.
What can I eat and drink before CoLyte?
Three days before your procedure, avoid raw fruits and vegetables, whole-wheat and multigrain products, beans, nuts, popcorn and seeds. The day before, have clear liquids only: water, coffee, tea, broth, sodas, apple juice, sports drinks, gelatin, popsicles and hard candy. No solid food, no milk, and nothing red or purple.
What if I feel sick while taking CoLyte?
Slow down your prep intake and walk around until the nausea settles, then continue. Baby wipes or a cleansing lotion can reduce irritation during the prep. If you vomit repeatedly or cannot finish the prep, call (346) 340-4414.
When do I have to stop eating and drinking?
Clear liquids are allowed until 3 hours before your appointment arrival time. From 3 hours before arrival, take absolutely nothing by mouth, including gum, hard candy and breath mints. Prescription medicines you have been told to take may be taken with water up to 3 hours before arrival.
I have diabetes or take a GLP-1 medicine. What changes?
Read the GLP-1 and diabetic prep sections on this page. Weekly GLP-1 medicines are held 7 days before the procedure and daily ones on the day of the procedure, as instructed. Do not take oral diabetes pills on prep day or procedure day, reduce insulin as described, and contact your diabetes doctor for instructions if you use an insulin pump.
United Gastroenterology Associates Offices
Questions about your prep or appointment can be answered by either office. Your arrival location and time are in your appointment instructions.
United Gastroenterology Associates – Katy
Katy Freeway (I-10) near the Grand Parkway
- Address: 23920 Katy Freeway, Suite 555, Katy, TX 77494
- Phone: (346) 340-4414
- Hours: Monday–Friday, 8:30 AM–5:00 PM (closed 12:00–1:30 PM for lunch; last appointment 4:30 PM)
United Gastroenterology Associates – Cypress
Northwest Freeway (US-290) in Cypress
- Address: 21216 Northwest Freeway, Suite 640, Cypress, TX 77429
- Phone: (346) 340-4414
- Hours: Monday–Friday, 8:30 AM–5:00 PM (closed 12:00–1:30 PM for lunch; last appointment 4:30 PM)
Ready to Start Your CoLyte Prep?
Read the General Colonoscopy Instructions first, follow the CoLyte steps above, and call (346) 340-4414 with any questions or difficulty during the prep.
Sources
- U.S. National Library of Medicine. DailyMed: GoLYTELY (PEG-3350 and electrolytes for oral solution) prescribing information and medication guide. dailymed.nlm.nih.gov
- U.S. National Library of Medicine. DailyMed: CoLyte (PEG-3350 and electrolytes for oral solution) prescribing information and medication guide. dailymed.nlm.nih.gov
- American Society for Gastrointestinal Endoscopy. Understanding Bowel Preparation. asge.org
These are the patient preparation instructions of United Gastroenterology Associates for CoLyte, TriLyte and GoLytely. They do not replace the personal instructions you receive from your doctor. Do not change any medicine without medical guidance. For a medical emergency, call 911. Last updated October 21, 2026.