With antibiotics, most bladder infections start easing within a day or two and clear in under a week.
Untreated, some resolve but many smolder for weeks - and the risk that justifies prompt treatment is the climb to the kidneys, which turns a nuisance into fever, back pain, and hospitalization risk. Fever plus back or side pain on top of urinary symptoms is a same-day call. The CDC's standing advice: take antibiotics exactly as prescribed, finish the course, and drink plenty of fluids.
What to do
Common questions
How long does a UTI last?
With treatment, fast: most uncomplicated bladder infections start easing within a day or two of starting antibiotics and clear fully in under a week, with three-to-seven-day courses standard. The CDC's guidance is to take the antibiotic exactly as prescribed and finish it, drink plenty of fluids, and call if you are not improving. Without treatment, the answer gets unpredictable: a minority of mild UTIs resolve on their own, but many smolder for weeks - and the risk that justifies treating promptly is ascent: a bladder infection that climbs to the kidneys becomes pyelonephritis, which brings fever, back or side pain, nausea, and a real hospitalization risk. So the fever-plus-back-pain combination on top of urinary symptoms is a same-day call, not a wait-and-see. The other reason to get the diagnosis rather than self-treating: burning with urination overlaps with STIs and vaginal infections that need entirely different treatment, so a first episode, recurrence, or anything unusual deserves the urine test. Pymander, a free AI doctor available 24/7 by text, can help you sort urinary symptoms before you head in.