A fever that lasts more than three days, reaches 103 degrees or comes with troubling symptoms warrants medical attention, according to University of Rochester Medicine's guidance for adults.
In its fever explainer, virtual urgent care physician assistant Marque-Ann Mattle explains how to measure a temperature, manage discomfort and recognize warning signs.
The guidance is dated Oct. 8, 2025. It describes general fever care rather than reporting a new outbreak or measuring how much flu is circulating locally.
What a fever does — and does not — mean
UR Medicine generally defines a fever in adults as a temperature of 100.4 degrees Fahrenheit or higher. A reading above 98.6 degrees alone does not necessarily meet that definition: normal body temperature varies among people and throughout the day, often running lower in the morning and higher in the afternoon.
Flu, COVID-19 and strep throat are among the infections that can cause fever. During an infection, a rise in temperature is part of the body's immune response, making conditions less favorable for invading germs, the health system explains.
Fever does not establish which illness someone has, and the absence of fever does not rule out flu. Influenza can cause coughing, a sore throat, body aches, headache and fatigue without an elevated temperature.
Other possible causes of elevated temperature include chronic conditions such as cancer or autoimmune disease, reactions to certain medications and some vaccines. Physical activity can temporarily raise temperature, which should return toward normal during recovery. Heat exhaustion or heat stroke requires a different response: high temperature with signs of heat illness calls for immediate medical care.
Some people develop a fever during the first day or two after vaccination as their immune system responds. The flu vaccine cannot cause influenza, the guidance says.
Symptoms accompanying a fever can include chills, body aches, headache, hot or dry skin, a faster heart rate, reduced appetite, nausea, vomiting or a rash.
Measuring temperature and managing discomfort
UR Medicine describes oral and rectal thermometers as generally the most accurate. Ear and forehead thermometers can provide useful readings when used correctly. Parents should follow a thermometer's instructions and ask a pediatrician about measuring or interpreting a child's temperature rather than applying adult guidance without checking.
Many illness-related fevers can be managed at home with rest and fluids. The explainer also describes lukewarm baths and cool, damp washcloths on the forehead, wrists or back of the neck as comfort measures.
Ibuprofen or acetaminophen may relieve discomfort when appropriate. Medication is not automatically necessary for every adult fever that causes no discomfort, but the temperature should continue to be monitored, according to the guidance.
The familiar advice to starve a fever is not helpful, UR Medicine says. The body still needs food and fluids while fighting illness. Small, nutritious meals may be easier to tolerate when appetite is reduced, and drinking fluids helps prevent dehydration.
When to seek care
Although illness-related fevers often last three or four days, the explainer advises contacting a health care provider when a fever lasts longer than three days, reaches 103 degrees or higher, or does not decrease with ibuprofen or acetaminophen. Difficulty breathing or urinating also requires medical attention.
People with fever should contact their provider if they recently had surgery, have a weakened immune system or recently traveled somewhere a serious infectious disease is common. Anyone uncomfortable managing a fever at home or uncertain about symptoms should seek advice rather than wait for a particular temperature threshold.
UR Medicine advises immediate emergency care for fever accompanied by a seizure, lethargy, a stiff neck, rash or confusion, or for a high temperature with symptoms of heat illness.
FingerLakes1.com is the region’s leading all-digital news publication. The company was founded in 1998 and has been keeping residents informed for more than two decades. Have a lead? Send it to news@fingerlakes1.com.
