Rifaximin dosage guide: what to take, how often, and why it matters

If you’ve been prescribed Rifaximin, you probably want to know the exact amount to take. The good news is the dosing is pretty straightforward once you know your condition, age, and any kidney issues. Below we break down the most common dosing schedules, give you a quick reference table, and share practical tips to keep side effects low.

Adult dosing for the main uses

Traveler’s diarrhea – The standard adult dose is 550 mg taken three times a day for three days. Take the pills with or without food; just keep the timing consistent.

Hepatic encephalopathy – Adults usually get 550 mg two to three times daily for up to 12 weeks, based on doctor guidance. If you have liver disease, your doctor may adjust the length of treatment.

Irritable bowel syndrome with diarrhea (IBS‑D) – The typical regimen is 550 mg twice daily for 14 days, then a break. Some doctors repeat the cycle if symptoms return.

For all adults, if you have reduced kidney function (creatinine clearance under 30 ml/min), the dose may be lowered to 400 mg twice daily. Always confirm with your healthcare provider before changing anything.

Kids, special cases, and practical tips

Pediatric dosing – Rifaximin isn’t approved for most children under 12, but when used off‑label, doctors often base the dose on weight: about 15 mg per kilogram of body weight, given twice daily. For a 20‑kg child, that works out to roughly 300 mg twice a day.

Adjusting for other conditions – If you’re also taking antibiotics that affect gut bacteria, talk to your doctor. Rifaximin stays mostly in the gut, so drug interactions are limited, but it’s still worth checking.

How to take the pill – Swallow the tablet whole; don’t chew or crush it unless your doctor says otherwise. Use a full glass of water and try to take each dose at the same times each day to keep blood levels steady.

Missing a dose – If you realize a dose is missed within a couple of hours, take it right away. If it’s almost time for the next dose, skip the missed one—don’t double up.

Common side effects – Most people only experience mild stomach upset or nausea. If you get severe diarrhea, rash, or signs of an allergic reaction, seek medical help.

Below is a quick reference you can print or bookmark:

Remember, the exact plan for you depends on your doctor’s assessment. Never start, stop, or change the dose without professional advice.

Keeping a small notebook of when you take each pill can help you stay on track, especially if you have a multi‑day course. Pair the medication with plenty of fluids and a balanced diet to reduce stomach irritation.

Got questions about your Rifaximin prescription? Talk to your pharmacist or doctor—clarifying doubts early saves hassle later.