Severe UTI symptoms include a persistent, urgent need to urinate, often accompanied by a burning sensation. Urine may appear cloudy, bloody, or have a strong odor. Sufferers often pass small amounts of urine frequently. Pelvic pain is common in women, while both genders might experience lower abdominal or flank pain. Fever, chills, nausea, and vomiting can indicate a more serious infection that has spread to the kidneys. Pain in the lower back or side is also a significant symptom. Immediate medical attention is essential to prevent complications from a severe UTI.