Polyethylene Glycol 3350 (PEG 3350): What it is and when to use it

Polyethylene glycol 3350, often called PEG 3350 or sold under brand names like Miralax, is an over-the-counter osmotic laxative. It holds water in the stool to soften it and help bowel movements happen more easily. People use it for occasional constipation, to avoid straining, or when a doctor recommends a gentle long-term option.

How to use PEG 3350

The common adult dose for occasional constipation is about 17 grams (usually one capful or one scoop) mixed into 4–8 ounces of water, juice, or another noncarbonated drink once a day. Stir until dissolved and drink right away. Expect effects in 12 to 72 hours—it’s not usually an immediate fix. For children, elderly people, or long-term use, follow the package instructions or your doctor’s directions.

If a healthcare provider prescribes PEG 3350 for bowel prep before a procedure, the dose and instructions will be different—follow that plan exactly. Don’t mix it with hot liquids and don’t add it to carbonated drinks; it tastes best when dissolved in room-temperature liquid.

Side effects, warnings, and when to call your doctor

Common side effects are mild: bloating, gas, nausea, and loose stools. If diarrhea occurs, stop use and sip clear fluids to avoid dehydration. Serious allergic reactions are rare but need immediate attention—look for hives, swelling, or difficulty breathing.

Do not use PEG 3350 if you have a bowel obstruction, severe abdominal pain, or an undiagnosed sudden change in bowel habits. If you have inflammatory bowel disease, kidney disease, or heart failure, check with your doctor before starting it. Pregnant or breastfeeding? Ask your provider—many clinicians consider PEG 3350 low risk, but medical advice is best.

PEG 3350 is minimally absorbed into the body, so it has few drug interactions. Still, if you’re on prescription medicines or have electrolyte concerns, ask your pharmacist or doctor, especially for long-term daily use.

Use caution in older adults: monitor for dehydration and falls if diarrhea or weakness appears. If constipation lasts more than 2 weeks despite using PEG 3350, or if you notice blood in stool, fever, or severe pain, seek medical care promptly.

Storage is simple: keep the powder in a dry place at room temperature and seal the container between uses. It’s sold OTC at pharmacies and online—buy from reputable sellers and check expiration dates.

Quick practical tips: start with the recommended dose, give it a couple of days to work, drink plenty of fluids, and increase fiber and gentle activity to help regularity. When in doubt, reach out to your healthcare provider—especially for kids, long-term use, or if you have other medical problems.