UTI vs. Kidney Infection: How to Tell the Difference

A urinary tract infection (UTI) and a kidney infection (pyelonephritis) involve the same urinary system but differ in location, severity, and treatment urgency. A lower UTI (cystitis) affects the bladder and urethra. Symptoms include burning during urination, frequent urination, cloudy or strong-smelling urine, and pelvic discomfort. Lower UTIs are usually uncomplicated and treatable with a short course of oral antibiotics. A kidney infection occurs when bacteria travel upward from the bladder to one or both kidneys. It is a more serious condition. Symptoms include everything above plus high fever and chills, severe back or flank pain (usually one-sided), nausea and vomiting, and confusion or extreme fatigue. Key differences: a UTI typically causes localized bladder symptoms without fever. A kidney infection usually causes systemic symptoms - fever, back pain, and feeling generally unwell. Kidney infections can become dangerous and may require intravenous antibiotics if severe. When to seek urgent care: if you have UTI symptoms plus fever above 38.5°C, severe flank pain, or persistent vomiting, seek medical attention promptly. Untreated kidney infections can lead to sepsis. An initial assessment can be done through telehealth if you are unsure. *This article is for informational purposes only.*

This article is for informational purposes only and does not constitute medical advice. Content reviewed by licensed Canadian physicians. Last updated February 2026.