Polyethylene Glycol 3350: What It Is and When to Use It

If you’ve ever struggled with occasional constipation, you may have heard of polyethylene glycol 3350, often called PEG 3350. It’s the active ingredient in many over‑the‑counter laxatives like MiraLAX. Doctors also use it to clean out the colon before procedures such as colonoscopy. In short, PEG 3350 is a powder you mix with water that pulls water into your intestines, making stool softer and easier to pass.

How PEG 3350 Works as a Laxative

PEG 3350 is an osmotic laxative. That means it doesn’t stimulate the gut muscles directly; instead, it creates an environment that keeps water inside the bowel. More water means the stool swells, moves more smoothly, and you feel the urge to go. Because it works gently, most people experience a soft bowel movement within one to three days of starting the product.

It’s also non‑absorbing, so very little of the chemical enters your bloodstream. This makes it a good choice for people who need a mild, predictable effect without the cramping that stimulant laxatives can cause.

Safe Dosing, Side Effects, and Who Should Avoid It

For adults, the typical dose is 17 grams of powder (about one heaping tablespoon) mixed with 8 ounces of water, juice or another clear liquid. Drink the mixture right away and follow it with another glass of water. You can repeat the dose once a day for up to seven days, but most users need only one dose.

Kids 17 kg (about 37 lb) or heavier can take a lower dose—usually 0.5 grams per kilogram of body weight—mixed the same way. Always check the package instructions or ask a pharmacist before giving it to a child.

Common side effects are mild: bloating, gas, or a slight stomach ache. If you notice severe abdominal pain, vomiting, or blood in your stool, stop using it and call a doctor. Because PEG 3350 works by holding water in the bowel, it’s important to drink plenty of fluids while you’re using it.

People with kidney disease, an intestinal obstruction, or a history of severe dehydration should avoid PEG 3350 unless a doctor says it’s okay. Pregnant or nursing moms should also check with their health care provider before starting.

When using PEG 3350 for a colonoscopy prep, the dose is much higher—usually a whole packet mixed with 64 ounces of clear liquid over several hours. Follow your doctor’s schedule exactly, and don’t add milk, alcohol, or colored drinks because they can affect the test results.

Storing the powder is simple: keep it in a cool, dry place, sealed tightly. It’s stable for years, so you don’t have to worry about it going bad quickly.

In everyday life, most people take PEG 3350 only when they need occasional relief. If you find yourself needing it more than twice a month, talk to a health professional. Chronic constipation can be a sign of diet, lifestyle, or underlying health issues that need a broader approach.

Bottom line: polyethylene glycol 3350 is a safe, effective, and easy‑to‑use option for constipation and bowel prep when you follow the dosage directions and stay hydrated. Keep these tips in mind, and you’ll get relief without the hassle.