Before a colonoscopy, you drink only clear liquids for the full day leading up to your procedure, plus a prescribed bowel prep solution that flushes your colon clean. The rule of thumb is simple: if you can pour it into a glass and see through it, you can drink it. You’ll stop all liquids two to four hours before your scheduled procedure time.
Clear Liquids You Can Drink
Your clear liquid diet starts 24 hours before the colonoscopy. “Clear” doesn’t mean colorless. Liquids can have some color as long as you can see through them. Here’s what’s on the approved list:
- Water: plain, carbonated, or flavored
- Sports drinks: Gatorade or Powerade in yellow, green, or blue
- Broth: clear, fat-free bouillon or consommé
- Coffee or tea: black only, with sugar or sugar substitutes if you like
- Sodas: including dark ones like cola and root beer
- Fruit juice: strained, with no pulp (apple juice and white grape juice are common choices)
- Fruit-flavored drinks: lemonade, Kool-Aid, or fruit punch in approved colors
- Gelatin and popsicles: as long as they don’t contain fruit, milk, seeds, or nuts
- Alcohol: technically permitted, though not the best idea when you’re already losing fluids
Coffee drinkers, take note: you can have your morning cup, but absolutely no milk, cream, or non-dairy creamer. That restriction covers almond milk, soy milk, rice milk, and any other dairy alternatives. Sugar is fine. If it’s opaque, it’s off limits.
Colors to Avoid and Why
Skip any beverage, gelatin, or popsicle made with red, purple, blue, or orange dyes. These dyes can coat the lining of your colon and look similar to blood or abnormal tissue during the procedure, making it harder for your doctor to spot actual problems. This means no red Gatorade, no grape juice, no cherry gelatin, and no orange soda. Stick with yellow, green, or clear versions of flavored drinks.
The Bowel Prep Solution
The clear liquid diet keeps you hydrated, but the heavy lifting comes from a prescribed laxative solution your doctor will specify. This is the drink people dread, and it works by pulling water into your colon so everything flushes out completely. Your colon needs to be totally empty for the doctor to see the tissue clearly.
The most commonly prescribed formulas use a polymer-based laxative (you’ll see brand names like GoLYTELY, MiraLAX, or MoviPrep on your prescription). These contain a large molecule your body can’t absorb, which draws fluid into the bowel and triggers a thorough cleanout. Other formulas use mineral salts or a stimulant laxative that speeds up the muscle contractions in your intestines. Brand names in this category include Suprep, Clenpiq, and SUTAB.
Older prep regimens required drinking a full gallon (4 liters) of solution, which was notoriously hard to get through. Many doctors now prescribe low-volume options that cut that in half to about 2 liters, combined with other laxative ingredients. If you’ve heard horror stories about drinking an ocean of salty liquid, it’s worth asking your doctor about a lower-volume option.
When and How to Drink the Prep
Most prep regimens today are split into two doses, and this matters. The current standard recommended by gastroenterology guidelines is split-dose preparation: you drink the first half the evening before your colonoscopy and the second half early on the day of the procedure. This approach produces a cleaner colon than drinking the entire solution the night before. For afternoon colonoscopies, a same-day regimen (both doses in the morning) is an acceptable alternative, but for morning procedures, splitting the doses is clearly better.
A typical schedule looks something like this: the day before your colonoscopy, you start your clear liquid diet in the morning, drinking about 8 ounces of clear fluids every hour to stay hydrated. Around 6 p.m., you begin the first half of your prep solution, drinking an 8-ounce glass every 15 minutes until you’ve finished that portion. Then, roughly six hours before your scheduled procedure, you drink the second half on the same schedule. Between doses, you can keep sipping approved clear liquids like sports drinks, broth, or water.
The prep solution contains electrolytes specifically to help prevent dehydration, since you’ll be losing a significant amount of fluid. Drinking sports drinks between doses adds extra electrolytes and can also help mask the taste of the prep if you alternate sips.
When to Stop Drinking Entirely
You must stop consuming all liquids, including water, at least two to four hours before your procedure. Your doctor’s office will give you a specific cutoff time based on your appointment. This restriction exists because you’ll receive sedation during the colonoscopy, and having liquid in your stomach during sedation carries a risk of aspiration. Follow your specific instructions closely on this one, because showing up without meeting the cutoff can mean your procedure gets postponed.
Tips for Getting Through the Prep
The prep solution is the hardest part of the entire colonoscopy experience for most people. Chilling it in the refrigerator makes it more tolerable. Drinking it through a straw placed toward the back of your tongue helps bypass some of your taste buds. Sucking on a lemon drop or hard candy (no red or purple) between glasses can cut the aftertaste. Some people find that chasing each glass with a sip of ginger ale or lemonade helps.
Stay close to a bathroom once you start the prep. Most people begin having bowel movements within one to three hours of the first dose, and the trips become frequent. Keep your clear liquid intake steady throughout the process. If you feel nauseated, slow down for 15 to 30 minutes before resuming. You’ll know the prep is working when your bowel movements become clear or light yellow, like urine. That’s the goal.