Can Urinary Tract Infections Cause Fever? Signs, Risks, and Treatment Explained
While many people associate urinary tract infections (UTIs) with symptoms like frequent urination, urgency, and burning during urination, fewer realize that some UTIs can lead to more serious complications—including fever. In particular, when the infection spreads beyond the lower urinary tract and reaches the upper urinary system, such as the kidneys or renal pelvis, it can trigger systemic symptoms like high fever, chills, and even life-threatening conditions.
When a UTI Becomes More Serious: Upper Urinary Tract Infection
An upper urinary tract infection—commonly known as pyelonephritis—occurs when bacteria travel from the bladder up into the kidneys. Unlike simple bladder infections, kidney infections involve more virulent strains of bacteria that are capable of entering the bloodstream. This invasion can result in bacteremia (bacteria in the blood) or toxemia (toxins in the blood), both of which activate the body's immune response and release powerful pyrogens—substances that cause fever.
Symptoms That Signal a Kidney Infection
If someone initially experiences typical UTI symptoms such as painful urination and increased frequency but then develops sudden chills, high fever (often above 101°F or 38.3°C), nausea, vomiting, or flank pain, it may indicate that the infection has progressed to the kidneys. A key clinical sign is tenderness when the area over the kidneys (the costovertebral angle) is tapped—a symptom known as costovertebral angle tenderness (CVAT).
In such cases, immediate medical evaluation is crucial. Delayed treatment increases the risk of sepsis, a severe and potentially fatal condition where the body's response to infection causes widespread inflammation, organ failure, and shock.
Diagnosing Severe Urinary Tract Infections
To confirm an upper UTI, healthcare providers typically order lab tests. These include urinalysis showing elevated white blood cells (pyuria), a rapid rise in blood-based markers like white blood cell count, and significantly increased C-reactive protein (CRP) levels—an indicator of systemic inflammation.
Imaging studies such as ultrasound or CT scans may also be used if complications are suspected, especially in patients who don't respond quickly to initial treatment. Blood cultures might be taken to check for bacteremia, particularly in those with high fevers or signs of toxicity.
Recommended Treatment and Recovery Timeline
Patients diagnosed with acute pyelonephritis are often hospitalized for intravenous antibiotic therapy, especially if they're unable to keep down oral medications due to vomiting or have signs of dehydration or septic shock. Broad-spectrum antibiotics—such as high-dose intravenous cephalosporins—are commonly administered initially.
Antibiotic selection is later adjusted based on urine culture and sensitivity testing, ensuring targeted treatment against the specific pathogen. The standard course of treatment lasts approximately two weeks. Even if symptoms improve within 7 to 10 days, it's essential not to stop medication prematurely. Completing the full course helps prevent recurrence and reduces the risk of developing antibiotic-resistant strains.
Follow-up testing—including repeat urinalysis, blood work, and CRP levels—is recommended after treatment to confirm that all infection markers have returned to normal before discontinuing care.
Prevention and When to Seek Emergency Care
Individuals with recurrent UTIs, diabetes, kidney stones, or structural abnormalities in the urinary tract are at higher risk for complicated infections. Staying well-hydrated, practicing good hygiene, and seeking prompt treatment for early UTI symptoms can help reduce this risk.
Anyone experiencing high fever, shaking chills, back pain, or confusion following a UTI should seek emergency medical attention immediately. Early intervention not only improves outcomes but can be lifesaving in cases of severe kidney infection or sepsis.