The day before a colonoscopy, you’ll need to stick to clear liquids, meaning anything you can see through at room temperature. This includes water, broth, plain gelatin, pulp-free juices, tea, coffee, sports drinks, and certain sodas. The goal is to empty your colon completely so your doctor has an unobstructed view during the procedure.
The Full List of Allowed Clear Liquids
The simplest test: hold it up to the light. If you can see through it, it’s likely fine. Here’s what qualifies:
- Water: plain, carbonated, or flavored
- Broth: chicken, beef, or vegetable bouillon and consommé (fat-free, with no solid pieces)
- Juices without pulp: apple juice, white grape juice, cranberry juice, lemonade
- Tea and coffee: black only, with no milk, cream, or nondairy creamer
- Sodas: ginger ale, Sprite, cola, root beer
- Sports drinks: Gatorade, Pedialyte, or similar electrolyte beverages
- Gelatin: plain Jell-O without any fruit pieces
- Popsicles: no fruit bits, pulp, yogurt, or cream
- Honey, sugar, and hard candy: lemon drops, peppermint rounds
You can add sugar or honey to your tea or coffee. What you cannot add is anything that makes the liquid cloudy: milk, cream, half-and-half, or nondairy creamer all disqualify it.
Avoid Red and Purple Colors
Most prep instructions specifically ban red and purple liquids, including red Jell-O, grape juice, red sports drinks, and cherry popsicles. These dyes can coat the lining of your colon and look like blood or inflammation during the exam, making it harder for your doctor to spot actual problems. Stick to yellow, green, or clear/white options when choosing gelatin, popsicles, and sports drinks.
No Alcohol During Prep
Even though some alcoholic drinks are technically clear, alcohol is off the list. It dehydrates you at a time when your body is already losing significant fluid from the bowel prep solution. Skip it entirely in the 24 hours before your procedure.
The Low-Fiber Phase Before Clear Liquids
The clear liquid day doesn’t come out of nowhere. Most gastroenterologists recommend switching to a low-fiber diet five to seven days before the procedure, and at minimum two to three days before. This transition phase makes the final prep more effective because there’s less bulk in your colon to clear out.
During this low-fiber phase, you can still eat real meals. Good options include white rice, refined pasta, eggs, chicken, fish, cooked carrots, potatoes without skin, bananas, soft cantaloupe, yogurt, cheese, and white bread. What you’re avoiding is anything that leaves residue behind: whole grains, raw vegetables, salads, nuts, seeds, corn, popcorn, beans, and dried fruit. You should also stop taking iron or fiber supplements at least three days before the exam, as iron can darken the colon lining and obscure the view.
When to Start and Stop
The switch to clear liquids only happens 24 hours before your scheduled procedure. So if your colonoscopy is at 10 a.m. on Wednesday, you’d begin the clear liquid diet by 10 a.m. on Tuesday. You’ll also be drinking the bowel prep solution during this window, which is the part most people find unpleasant, but the clear liquids in between can help you stay comfortable.
Most facilities ask you to stop drinking all liquids two to three hours before your procedure time. Your specific instructions may vary, so check the paperwork your doctor’s office provides.
Staying Comfortable on Clear Liquids
Twenty-four hours without solid food is manageable, but it helps to plan ahead. Broth is your best friend here: it’s warm, savory, and provides sodium your body is losing during prep. Alternating between broth and sports drinks helps maintain your electrolyte balance, which prevents the headaches, dizziness, and fatigue that come with dehydration.
Hard candy and honey in your tea can keep your blood sugar from dropping too low. Gelatin and popsicles give you something to “eat” that feels more substantial than drinking alone. Many people find it easier to sip small amounts continuously throughout the day rather than trying to drink large volumes at set meal times.
Extra Considerations for Diabetes
If you have diabetes, the clear liquid phase requires closer attention. You need enough carbohydrates to prevent your blood sugar from crashing, but not so much that it spikes. A reasonable target is about 45 grams of carbohydrates at mealtimes and 15 to 30 grams for snacks, using clear fluids that contain sugar or electrolytes.
Monitor your blood sugar before every meal and at bedtime the day before the procedure, and every four hours starting the morning of. If your levels drop too low, apple juice or glucose tablets can bring them back up quickly. If they run high, switch to sugar-free clear fluids. Bring your glucose meter, test strips, and a low blood sugar treatment like juice boxes or dextrose tablets with you on procedure day. Your care team will check your levels before sedation begins.