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 August 2026.