How long does a uti last?

Varies.: The length of time it takes to clear a urinary tract infection depends on the burden of the infection & how quickly appropriate antibiotics are started. Uncomplicated utis are treated with 3 days of antibiotics, and symptoms subside quickly and usually disappear by 7 days. Complicated utis including kidney infection, foreign bodies, and resistant organisms will increase the duration of treatment.

Usually < 7 days: Antibiotics, if effective, often clear the bladder of bacteria very quickly because they're concentrated in the urine. However, the inflammation (irritation) of the bladder walls may take days to resolve and the symptoms like burning with urination, frequent voiding, and pain. If these persist beyond one week or high fever or flank pain develops then contact your doctor.