For a colonoscopy, you drink two things: a prescribed bowel prep solution that clears out your colon, and a variety of clear liquids that keep you hydrated while the prep does its work. The day before your procedure, you’ll switch to a clear liquid diet and begin drinking the prep solution on a specific schedule. Here’s what to expect and how to get through it.
The Bowel Prep Solution
Your doctor will prescribe one of several bowel prep formulas designed to flush your colon completely clean. The traditional options, sold under names like GoLYTELY, NuLYTELY, and MiraLAX (mixed with a sports drink), use a compound called polyethylene glycol that pulls water into your intestines and triggers thorough emptying. These older formulas require drinking about 4 liters of fluid total, which is the part most people dread.
Newer, lower-volume preps have made things easier. Products like SUPREP, Clenpiq, and Sutab (a tablet form) use a different salt-based formula and require only 2 to 3 liters of fluid instead of 4. Some patients say these taste closer to a sports drink. Sutab, approved in 2020, lets you swallow tablets with water instead of drinking a flavored solution at all. Your doctor chooses which prep fits your health profile, but it’s worth asking about lower-volume options if the idea of drinking a gallon of liquid feels overwhelming.
How the Drinking Schedule Works
Most doctors now recommend a “split dose” approach, meaning you drink half the prep solution the evening before your colonoscopy and the second half early on the morning of the procedure. For a morning appointment, you’d typically finish the second dose about four hours before your scheduled arrival time, drinking one 8-ounce glass every 10 minutes until it’s gone.
Split dosing produces a cleaner colon than drinking everything the night before, which means your doctor gets a better view and you’re less likely to need a repeat procedure. It does mean setting an early alarm, but most people find it more tolerable than forcing down the entire volume in one sitting.
Clear Liquids You Can Drink
Starting the day before your colonoscopy, you’ll eat no solid food and drink only clear liquids. “Clear” means you can see through it. That gives you more options than you might expect:
- Water: plain, carbonated, or flavored
- Juices without pulp: apple juice, white grape juice
- Broth: clear, fat-free chicken, beef, or vegetable broth
- Sports drinks: Gatorade, Powerade (in approved colors)
- Sodas: Coke, Pepsi, ginger ale, Sprite, root beer
- Coffee or tea: black only, no milk, cream, or creamers
- Fruit-flavored drinks: lemonade, fruit punch (in approved colors)
- Gelatin and popsicles: in approved colors
- Honey or sugar: added to any of the above
Between prep doses, you can drink as many of these clear liquids as you want, and you should. The prep works better when you’re well hydrated, and extra fluids help replace what you’re losing.
Colors and Drinks to Avoid
Red, blue, and purple dyes can coat the lining of your colon and mimic the appearance of blood or abnormal tissue during the exam. Avoid any drink, gelatin, or popsicle in those colors. That rules out red Gatorade, grape juice, cranberry juice, blue raspberry anything, and purple Kool-Aid. Orange is also restricted by some doctors, so check your specific instructions.
Beyond color restrictions, skip all milk and dairy products, alcohol and beer, and anything with pulp or solid particles. Smoothies, protein shakes, and orange juice with pulp are all off the table. If you can’t see through it, don’t drink it.
The Morning Cutoff
After you finish your second prep dose on the morning of the procedure, you can typically continue sipping clear liquids until about two hours before your scheduled arrival time. After that window closes, nothing goes in your mouth. Not water, not gum, not a breath mint. Anything in your stomach when you receive sedation creates a safety risk, and your procedure will be delayed or canceled if you don’t follow this rule. Your doctor’s office may give you a slightly different cutoff, so follow their specific instructions over the general guideline.
Making the Prep Easier to Drink
The prep solution’s taste is the biggest hurdle for most people. A few strategies make a real difference. Drinking the solution ice cold dramatically improves the experience. If the jug doesn’t fit in your fridge, pour each glass over ice or fill a thermos with ice and add the prep as you go.
Using a straw helps bypass your taste buds and makes each glass go down faster. You can also skip the flavoring packet that comes with your prep and substitute your own, like flavored electrolyte powder or a lemonade packet, as long as you avoid red, blue, or purple dyes. One lesser-known trick: place a menthol candy or lozenge under your tongue while you drink. It blocks much of the prep’s flavor. Choose a candy that’s clear or green, not red or purple.
Drinking extra clear liquids between prep doses also helps dilute the taste lingering in your mouth. Sipping chicken broth, ginger ale, or apple juice between glasses of prep gives your palate a break and keeps your electrolytes up. Many people find that alternating a glass of prep with a glass of something they actually enjoy makes the whole process far more manageable.
Staying Hydrated Through Prep
The prep pulls a large volume of water through your intestines, which means dehydration is a real concern. You’ll lose more fluid than you expect, and symptoms like dizziness, headache, and fatigue during prep often come down to not drinking enough. Sports drinks are especially useful here because they replace sodium and potassium along with fluid. Clear broth serves the same purpose and can feel more satisfying when you haven’t eaten solid food all day.
Aim to drink clear liquids steadily throughout the entire prep day, not just when you’re thirsty. By the time you feel thirsty, you’re already behind. The better hydrated you are going into the procedure, the easier your recovery will be afterward, since the sedation and the prep itself can both leave you feeling drained.