Overview
Fever means the body temperature is above a person’s usual range. It often happens when the immune system is fighting an infection, but it can also occur with heat-related illness, inflammatory conditions, reactions to medicines, or after some vaccinations. Fever itself is not the illness; it is a clue that something else may be going on.
Key Symptoms
A person with fever may feel hot, chilled, sweaty, tired, achy, or weak. Headache, reduced appetite, fast heartbeat, and thirst can also happen. In children, irritability, sleepiness, poor feeding, or fewer wet diapers may be important warning signs.
Causes and Risk Factors
Common causes include viral or bacterial infections such as colds, flu, stomach infections, and urinary infections. Fever can also be linked to heat exhaustion or heatstroke, certain medicines, autoimmune or inflammatory diseases, and some cancers. Risk can be higher in young children, older adults, people with chronic illness, travelers exposed to infections, and people with weakened immune systems.
Who Is Affected
Anyone can get a fever. Children often get fevers with common infections, while older adults may have fever that is mild or less obvious even during serious illness. People receiving chemotherapy, taking immune-suppressing medicines, or living with conditions that affect immunity may need quicker assessment.
Diagnosis and Tests
Healthcare professionals usually ask about symptoms, travel, sick contacts, medicines, and how the temperature was measured. They may check temperature, breathing, heart rate, hydration, and signs of infection. Depending on the situation, tests may include blood tests, urine tests, swabs, or imaging to look for the cause.
Treatment Categories
Treatment depends on the cause and the person’s age, symptoms, and medical history. Supportive care may include rest, fluids, and monitoring temperature and other symptoms. A healthcare professional may recommend treatment for the underlying cause, especially if a bacterial infection, heat illness, or another serious condition is suspected.
Living With It
Many short-lived fevers improve as the body recovers, but it is important to watch for changes. Keep track of temperature, how the person is acting, fluid intake, urination, and any new symptoms. Avoid overheating with heavy blankets or very hot rooms.
When to Seek Medical Care
Seek medical advice if fever lasts more than a few days, keeps coming back, or is accompanied by worsening pain, rash, dehydration, persistent vomiting, or signs of infection in one area such as the chest or urine. Infants younger than 3 months with a fever need prompt medical evaluation. People who are pregnant, older, or immunocompromised should also seek advice sooner.
When It May Be an Emergency
Get urgent medical help for fever with trouble breathing, blue lips, severe sleepiness, confusion, seizure, stiff neck, severe headache, chest pain, signs of severe dehydration, or a person who is difficult to wake. Emergency care is also needed if fever occurs with heat exposure and hot dry skin, fainting, or altered mental state. In infants and medically fragile people, severe illness can develop quickly.