What’s considered a fever in adults and when to worry
Humans – like all mammals – are warm-blooded, meaning our bodies stay warm, or at a fairly consistent temperature, even when the temperature of our surroundings change.
For most of us, our bodies tend to hover between 97 and 99 degrees Fahrenheit. But in certain circumstances, our body temperate rises, resulting in a fever.
What is a fever for adults?
The body’s normal temperature is between 97.7 degrees and 99.5 degrees.
But don’t worry if your temperature hits 99.8 degrees – you probably don’t have a fever.
99 degrees isn’t usually considered a fever. But if you have other symptoms like cough, congestion or a runny nose, you may be sick.
The medical community generally defines a fever as a body temperature above 100.4 degrees Farenheit.
Causes of a fever in adults
A fever is not an illness by itself. A fever is your body’s way of telling you that you’re fighting some sort of infection or sickness. Common causes of fevers in adults include a bacterial infection, like strep throat, or viral infection, like COVID-19, the flu or a cold. A fever can also happen if you have an allergic reaction to food or medicine.
Worried about a fever?
“Your body’s immune system creates a fever to fight off infection,” said Sarah Joseph, MD. As an internal medicine and pediatrics specialist, Dr. Joseph treats children and adults of all ages for a wide range of illnesses.
What is considered a low-grade fever
A body temp between 100.4 and 102.2 degrees is usually considered a low-grade fever. Though something like 101 degrees may seem high, it’s actually still considered a low-grade fever.
“If the temperature is not high, it doesn’t necessarily need to be treated with medication,” Dr. Joseph said.
A low-grade fever for an adult usually doesn’t require treatment, unless the fever is occurring in a very young infant, or if it’s accompanied by other worrisome symptoms, such as confusion or the inability to eat or drink without vomiting.
To bring down a fever without medication, Dr. Joseph suggests wearing minimal clothing or bathing in lukewarm or cool water. You should also be sure to drink plenty of fluids to keep your body hydrated.
And keep in mind that even a mild fever could be a sign of a contagious illness. Washing your hands and covering your cough are always good practices.
“In the age of respiratory illnesses like COVID-19, one of the things people should keep in mind is that if they are having any kind of fever that is persisting, they should probably go get tested for COVID-19 and the flu,” Dr. Joseph said.
When is a fever too high?
When body temperature rises above 102.2 degrees, it can be a sign of a more serious infection.
Most fevers will resolve in a few days, but Dr. Joseph says some circumstances could be a reason to see a provider, either in a primary care office or urgent care clinic.
Consider seeing a doctor if you have:
- A fever lasting longer than three to five days
- A fever that doesn’t respond to fever-reducing medications, such as acetaminophen or ibuprofen (Tylenol or Advil)
- Confusion
- Neck stiffness
- Sensitivity to light
“Another reason to seek medical attention is if you don’t feel right about how things are going,” Dr. Joseph said.
Rarely, a fever could be a sign of a medical emergency.
Call 9-1-1 or go directly to an emergency room if you have a fever and any of the following symptoms:
- Seizures
- Severe abdominal pain
- Pain or burning with urination
- Shortness of breath or chest pain
- Difficulty holding down fluids
- Severe headache
How to reduce fever in adults
If you have a fever due to a viral infection, like a cold, the flu or COVID-19, your fever will likely go away on its own.
But once you get to a 102 fever or 103 fever, you probably will feel uncomfortable. That’s when you should start to treat your symptoms. But even if you feel fine with your fever it’s still important to do these things:
- Rest
- Get plenty of fluid
- Avoid being around people. Even if you feel well, you can still be contagious.
- Take over-the-counter fever-reducing medicine as directed on the medicine label or as directed by your primary care provider
- Take a lukewarm bath or shower
Last Updated: February 11, 2025