Key takeaways: A urinary tract infection (UTI) is a common cause of fever in babies with no other clear source. Babies often don’t have classic symptoms; they may just have fever, fussiness, poor feeding, or vomiting. Diagnosis needs a properly collected urine sample. UTIs are treated with antibiotics, and some babies need imaging afterward.
UTIs in babies can be easy to miss because babies can’t describe symptoms.
Signs
- Fever without another clear cause (the most common sign).
- Fussiness or irritability.
- Poor feeding.
- Vomiting or diarrhea.
- Poor weight gain.
- Strong-smelling urine (not reliable on its own).
- In newborns: jaundice, low temperature, or sleepiness.
Who’s at Higher Risk
- Uncircumcised boys in the first year.
- Girls.
- Babies with urinary tract abnormalities, such as vesicoureteral reflux.
From the author
From First Breath to First Birthday is my month-by-month guide to your baby’s first year, written as a NICU and postpartum nurse. My book covers common first-year illnesses and the warning signs that mean it’s time to call the doctor, explained the way I’d explain them at the bedside.
How It’s Diagnosed
A urine sample is tested for signs of infection and sent for a culture.
- Catheter sample: a thin tube is placed briefly into the bladder. It’s the most reliable method in young babies.
- Bag samples can be contaminated and are less reliable for diagnosis.
Treatment
- Antibiotics, by mouth or sometimes IV, especially in young or very sick babies.
- Finish the full course.
- Most babies feel better within a couple of days.
Follow-Up Imaging
The AAP guideline recommends a kidney and bladder ultrasound after a first fever-related UTI in babies 2 to 24 months. Further tests are needed in some cases, such as abnormal ultrasound or repeat infections.
Prevention
- Change diapers often.
- Wipe front to back.
- Treat constipation.
Call your baby’s doctor right away if your baby: is under 3 months with a fever of 100.4°F or higher, has a fever with no clear cause, is feeding poorly, vomiting, or seems very unwell.
The Bottom Line
UTIs often show up as fever alone in babies. A catheter urine sample confirms it, and antibiotics treat it. Some babies need follow-up imaging.
Want more support for your baby’s first year? My book, From First Breath to First Birthday, is available on Amazon.
Related Articles
- Fever in a Newborn: Why 100.4°F Means Call Right Away
- Ear Infections: Signs, Treatment, and Watchful Waiting
- Meningitis in Babies: Warning Signs
Sources
- Subcommittee on Urinary Tract Infection, Steering Committee on Quality Improvement and Management. Urinary tract infection: clinical practice guideline for the diagnosis and management of the initial UTI in febrile infants and children 2 to 24 months. Pediatrics. 2011;128(3):595-610.
- American Academy of Pediatrics. Urinary tract infections in young children. HealthyChildren.org. https://www.healthychildren.org
- Pantell RH, Roberts KB, Adams WG, et al; Subcommittee on Febrile Infants. Evaluation and management of well-appearing febrile infants 8 to 60 days old. Pediatrics. 2021;148(2):e2021052228.
This article is for general education and is not a substitute for individualized medical advice. Always talk with your baby’s health care provider or your own provider about your specific situation. If you think your baby or you may have a medical emergency, call 911.
