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Bladder infection (UTI) in adults: the signs, when it is the kidneys, and antibiotics
For any adult with burning when they pee, needing to go again and again, pain low in the belly, or cloudy, bloody or strong-smelling urine. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK, part of the NIH) says a bladder infection is the most common kind of urinary tract infection (UTI), is most often caused by bacteria, and, if untreated, can spread to the kidneys. This page passes on, by name, what NIDDK says: the signs, the signs that it may have reached the kidneys, pregnancy, the urine test and culture, antibiotics and why to finish them, liquids and care at home, and repeat infections and prevention. It builds the words to say at a clinic, and prints a card for the visit.
A word with a dotted line under it, like this, opens its official definition, quoted from a U.S. government glossary.
Right now
- Fever and chills, nausea or vomiting, or pain in your back, side or groin can be signs of a kidney infection, and NIDDK says quick treatment is important. Get care today: your provider, an urgent care, a nurse line or the emergency room (ours).
- The person is confused, very hard to wake, fainting, or seems very sick: call 911 (ours). See also our page on sepsis.
- Burning when you pee, needing to go often, lower belly pain, or cloudy, bloody or strong-smelling urine: NIDDK says to contact a health care professional. If you are pregnant, call today (ours).
More help
- A child: A UTI in a baby or child · A baby or child: find the right page.
- Related: Sepsis · When it’s your kidneys · Kidney stones · Pregnancy and a new baby · Birth control · Menopause.
- Care and costs: When you need a doctor and can’t pay · When medicine costs too much · My medicines list · Symptom diary · Get ready for your appointment.
- In a crisis: Help right now (988, 911). All our free tools.
Kidneys, bladder or urine, and not sure this is the right page? The pages on this site for bladder infections, kidney stones, kidney disease and bedwetting, on one list.
This page and its wording were written with AI (Claude) for Scarlet Beast (our AI policy). No doctor or nurse has reviewed it. The facts were read on October 15, 2026 on NIDDK’s Bladder Infection (Urinary Tract Infection—UTI) in Adults pages (NIH): the overview, Definition & Facts, Symptoms & Causes, Diagnosis, Treatment and Eating, Diet, & Nutrition (last reviewed April 2024). Ours: getting care the same day for fever, chills, vomiting, or back, side or groin pain; calling 911 when the person is confused, very hard to wake, fainting or seems very sick; not using leftover or someone else’s antibiotics; calling back if you are not better or get worse on the antibiotic; saying if you are or could be pregnant and which antibiotics you are allergic to; asking when a culture result will come; that it is not your fault; asking about a lower-cost option; and the order of the steps. What we left out: antibiotic names, the two pain reliever names NIDDK gives, doses and numbers of days, and clinical pages for providers. This page is about adults; for a baby or child, see our child UTI page. This page saves nothing and loads no trackers.