Most people know a fever is an abnormal rise in body temperature – and that a high temperature can have a variety of causes. On the other hand, there’s confusion as to what temperature is considered to be a fever. Here are some guidelines for understanding an elevated temperature in children and adults.
What is Considered a Fever in Adults?
A fever is present when an adult has a rectal temperature of 100.8 degrees Fahrenheit or above. When the temperature is taken by mouth, a temp above 99.9 degrees Fahrenheit is a fever. In reality, body temperature can vary depending upon the person, how hot or cold their environment is, and their activity level, although for most people temperatures above these levels are abnormal.
What is a Fever in Children?
As in adults, children have a fever when their body temperature climbs above 100.8 degrees Fahrenheit – measured rectally. Children have more normal variations in temperature than adults with some kids experiencing elevations in temperature up to 100.3 degrees Fahrenheit late in the day if they’re especially active or in a warm environment.
When is a Fever in Children Concerning?
A fever is concerning, not so much because it’s harmful, but because it can be a sign of serious illness. Some experts recommend not treating a fever in children because it helps to boost the body’s ability to destroy bacteria and viruses – and may speed up recovery from illness.
It’s important to look at fever in the context of other symptoms in a child. If a child looks lethargic, is complaining of pain, isn’t eating, has a headache, vomits repeatedly, has burning with urination, complains of a sore throat, or simply looks ill – mom or dad should call a doctor.
Age is also a factor. Infants under three months should see a doctor for any fever, and children up to six months of age need medical attention if they have a fever above 101 degrees Fahrenheit. Parents should call a doctor if infants over six months have a temperature greater than 103 degrees Fahrenheit. Also, a fever that doesn’t go away in seven days – or occurs in a child who has medical problems needs evaluation.
What about Fever in Adults?
As with children, it’s important to look at fever in the context of other symptoms. An adult who has abdominal pain, a stiff neck, a bad headache, shortness of breath, chest pain, repeated vomiting, or looks disoriented needs a doctor’s care if they have a fever. If a fever persists for more than a week or climbs above 103 degrees Fahrenheit, it needs medical attention.
What Temperature is Considered a Fever: The Bottom Line?
A fever is not usually dangerous, and it’s unlikely to cause brain damage. It’s the body’s response to illness. It’s important to consider it in the context of whatever symptoms are found with it when deciding whether it needs evaluation.
Merck Manual. Eighteenth edition. 2006.