Before a colonoscopy, you’re limited to clear liquids for most of the day before your procedure. Clear liquids are anything you can see through: water, clear broths, apple juice, tea, certain sodas, sports drinks, and gelatin. The main rule beyond “clear” is avoiding anything red, blue, or purple, because those dyes can stain the lining of your colon and be mistaken for abnormalities during the exam.
What Counts as a Clear Liquid
A clear liquid is anything transparent or translucent at room temperature. You don’t have to stick to water. The full list is more varied than most people expect:
- Water: plain, carbonated, or flavored (like LaCroix or similar)
- Fruit juices without pulp: apple juice and white grape juice are the go-to options
- Fruit-flavored drinks: lemonade, fruit punch, Kool-Aid, and Hi-C, as long as the color is allowed
- Carbonated drinks: Coke, Pepsi, root beer, ginger ale, Sprite, and other sodas are all fine
- Sports drinks: Gatorade, Powerade, or Pedialyte in yellow, green, or clear varieties
- Broth or bouillon: chicken, beef, or vegetable, strained so there are no noodles, vegetables, or bits of fat floating in it
- Coffee and tea: black only, with no milk, cream, or non-dairy creamer of any kind
- Gelatin (Jell-O): in approved colors only
- Ice pops and Italian ice: as long as they’re not red, blue, or purple and don’t contain fruit pieces or cream
- Honey and sugar: fine to add to tea or coffee for flavor
The test for whether something qualifies is simple: hold it up to light. If you can’t see through it, skip it.
Colors to Avoid and Why
Red, blue, and purple liquids are off-limits across the board. These dyes can coat the inside of your colon and look like blood, inflammation, or other abnormalities when the doctor is examining the tissue. That means no red Gatorade, no grape juice, no cherry Jell-O, and no blue Powerade.
Some facilities also restrict orange-colored drinks. Cleveland Clinic, for example, lists orange alongside red and purple as prohibited. Your prep instructions may differ slightly, so check the specific sheet your doctor’s office gave you. When in doubt, stick with yellow, green, or completely clear options.
What’s Not Allowed
Several liquids that seem like they might qualify are actually off the table. Milk of any kind, including almond milk, soy milk, rice milk, and oat milk, is not a clear liquid. Neither is any creamer, dairy or non-dairy. Orange juice with pulp, smoothies, and tomato juice all fail the “see through it” test.
Alcohol is also prohibited. Most prep instructions call for stopping alcohol at least two days before your colonoscopy. Alcohol dehydrates you at a time when you’re already losing significant fluid from the bowel prep, and it can interact with the sedation you’ll receive during the procedure.
Bone broth is a gray area. If it’s thin, clear, and fully strained with no fat globules or particles, it generally works. But the thick, gelatinous bone broths that are popular right now often leave residue. A simple boxed chicken broth, strained, is a safer bet.
Coffee and Tea Rules
You can have coffee and tea, but they must be completely black. No milk, no cream, no non-dairy creamer, no butter, no collagen powder. Sugar and honey are fine. If you’re a heavy coffee drinker, this is worth knowing: skipping caffeine entirely on prep day can give you a withdrawal headache on top of everything else, so a few cups of black coffee can make the day significantly more bearable.
Staying Hydrated During Prep
The bowel prep solution itself will pull a large amount of water into your intestines, so dehydration is a real concern. Drinking only plain water can actually make this worse because you lose electrolytes (sodium, potassium) along with the fluid. Sports drinks like Gatorade or Pedialyte between doses of your prep solution help replace those electrolytes and keep you feeling less wiped out. Clear broth is another good source of sodium.
Many people underestimate how much fluid they need. A good target is to keep sipping clear liquids steadily throughout the day rather than drinking large amounts at once. If you start feeling lightheaded, nauseated, or develop a headache, increase your intake of electrolyte-containing liquids.
When to Stop Drinking
The day before your procedure, you’ll switch to clear liquids only (your prep instructions will specify the exact time, often starting the morning before). The final cutoff for all liquids, including water, is typically 2 hours before your scheduled procedure time. This is based on anesthesia safety guidelines from the American Society of Anesthesiologists: clear liquids leave your stomach within about 2 hours, and an empty stomach prevents complications during sedation.
Your specific facility may set the cutoff at 3 or 4 hours to build in a safety margin. Follow whatever time your doctor’s office gives you, and if you accidentally drink something inside that window, call them before your appointment rather than just showing up. They may need to delay the procedure.
If You Have Diabetes
The clear liquid phase is particularly tricky for people with diabetes. The day of prep is essentially a fasting day, and most clear liquids contain little to no carbohydrate unless you’re specifically choosing sugary options. This combination of minimal food intake and bowel prep can cause dangerous drops in blood sugar, especially if you’re taking insulin or medications that stimulate insulin production.
Recent recommendations suggest that people with diabetes should try to eat a low-fiber diet the day before the procedure instead of switching to an all-liquid diet so early. A breakfast of eggs with white toast or fish with white rice the morning before an afternoon prep, for example, provides steadier blood sugar than a day of broth and apple juice. During the clear liquid phase, include liquids with some sugar content, like juice or regular (not diet) sports drinks, and monitor your blood sugar more frequently than usual. Your doctor should give you specific instructions about adjusting your diabetes medications for prep day.