GaviLyte-G is a prescription powder that you mix with water to create a 4-liter bowel-cleansing solution. It’s used before colonoscopies and barium enema X-ray exams in adults. The solution works as an osmotic laxative, pulling water into your colon to flush it out so your doctor can get a clear view of the tissue inside.
What’s in the Solution
GaviLyte-G contains polyethylene glycol 3350 (PEG 3350) as its active ingredient, combined with a specific blend of electrolytes. When mixed with water to the full 4-liter volume, each liter contains 59 grams of PEG 3350, along with sodium sulfate (5,690 mg), sodium bicarbonate (1,690 mg), sodium chloride (1,470 mg), and potassium chloride (743 mg).
The PEG 3350 does the heavy lifting. It’s a large molecule that your body doesn’t absorb. Instead, it stays in your digestive tract and holds water there through osmotic pressure, essentially preventing your colon from reabsorbing fluid the way it normally does. The result is a large volume of watery stool that washes the colon clean. The electrolytes are there to replace the sodium, potassium, and other minerals that would otherwise be lost during this process, helping to keep your body’s chemistry stable.
How to Mix and Store It
The product comes as a dry powder in a large container with a fill line marked at 4 liters. You add lukewarm tap water up to that line, cap it tightly, and shake or mix until everything dissolves. Some versions of GaviLyte come with a flavor pack (like lemon). If you’re using one, add the flavor powder to the bottle before you add water, then shake well to incorporate it before reconstituting. No other ingredients, flavorings, or dyes should be added to the solution beyond what’s provided.
Once mixed, keep the solution refrigerated. It stays good for 48 hours. Discard anything left over after that window.
How You Drink It
The standard approach is to drink 8 ounces (one full glass) every 10 minutes. You continue at that pace until you’ve finished the entire 4 liters or until your bowel movements run completely clear, whichever comes first. That pace works out to roughly 45 minutes to an hour and a half of steady drinking, depending on how your body responds.
This is a lot of liquid in a short time, and most people find the experience uncomfortable. Chilling the solution helps with the taste. Drinking through a straw placed toward the back of your tongue can also reduce how much you taste it. Your doctor’s office will typically give you a specific schedule, sometimes splitting the dose into two sessions (one the evening before and one early the morning of your procedure).
Common Side Effects
Nausea, abdominal fullness, and bloating are the most frequently reported side effects, affecting up to 50% of people who take the solution. That’s a high rate, but it’s not surprising given the volume you’re drinking and the speed at which it moves through your system. These symptoms are usually temporary, peaking while you’re actively drinking and tapering off once you finish.
Cramping and general discomfort in your abdomen are also common. Most of what you experience is the solution doing exactly what it’s designed to do: flooding your colon with fluid and triggering repeated bowel movements. Expect to stay very close to a bathroom for several hours.
Who Should Not Take It
GaviLyte-G is not appropriate for everyone. People with a bowel obstruction, a perforated bowel, or a condition called toxic megacolon (a dangerous dilation of the large intestine) should not use this solution. If you have difficulty swallowing, a weakened gag reflex, or are prone to aspiration (inhaling liquid into your lungs), the rapid drinking schedule can pose a serious risk. Your prescribing doctor will screen for these conditions before recommending the prep.
People with kidney problems, heart failure, or seizure disorders need closer monitoring because the large fluid shifts involved can affect electrolyte levels. If you take other medications, the prep can interfere with absorption since it’s flushing your system, so your doctor may adjust the timing of your other prescriptions around the prep schedule.
What the Prep Day Looks Like
Before you start drinking the solution, you’ll typically switch to a clear liquid diet for the day. That means broth, clear juices (like apple juice), gelatin, popsicles, tea, and water. Solid food, dairy, and anything with red or purple dye are off the table because they can leave residue that mimics abnormalities during the colonoscopy.
Once you begin drinking the GaviLyte-G, bowel movements usually start within 30 minutes to an hour. They’ll progress from formed stool to loose, then watery, and eventually clear or light yellow. The goal is a completely clean colon. A well-prepped bowel makes it significantly easier for your doctor to spot polyps, inflammation, or other issues, and reduces the chance that you’ll need to repeat the procedure due to poor visibility.
Plan to set aside your entire evening (or morning, depending on the schedule) for the prep. Having wet wipes, barrier cream, and something to read or watch nearby makes the process more manageable. The prep is consistently rated as the worst part of getting a colonoscopy, but the procedure itself is typically quick and painless by comparison.