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A fever is when your body temperature is higher than normal, i.e. 37°C. It is caused by infections or other illnesses like flu, overheating, or dehydration. When you have a fever, you may also experience a hot, flushed face, headache, loss of appetite, body aches, shivering, sweating or weakness.
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Body temperatures vary slightly from person to person and at different times of day. The average temperature has traditionally been defined as 98.6 F (37 C). A temperature taken using a mouth thermometer (oral temperature) that's 100 F (37.8 C) or higher is generally considered to be a fever.
Depending on what's causing a fever, other fever signs and symptoms may include:
•Sweating
•Chills and shivering
•Headache
•Muscle aches
Infants and toddlers
A fever is a particular cause for concern in infants and toddlers. Call your baby's health care provider if your child is:
Children
There's probably no cause for alarm if your child has a fever but is responsive. This means your child makes eye contact with you and responds to your facial expressions and to your voice. Your child may also be drinking fluids and playing. Call your child's health care provider if your child:
Adults
Call your health care provider if your temperature is 103 F (39.4 C) or higher. Seek immediate medical attention if any of these signs or symptoms accompanies a fever:
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Typical body temperature is a balance of heat production and heat loss. An area in the brain called the hypothalamus (hi-poe-THAL-uh-muhs) — also known as your body's "thermostat" — monitors this balance. Even when you're healthy, your body temperature varies slightly throughout the day. It can be lower in the morning and higher in the late afternoon and evening.
When your immune system responds to disease, the hypothalamus can set your body temperature higher. This prompts complex processes that produce more heat and restrict heat loss. The shivering you might experience is one way the body produces heat. When you wrap up in a blanket because you feel chilled, you are helping your body retain heat.
Fevers below 104 F (40 C) associated with common viral infections, such as the flu, may help the immune system fight disease and are generally not harmful.
Fever or elevated body temperature might be caused by:
•A viral infection
•A bacterial infection
Children between the ages of 6 months and 5 years are at increased risk of a seizure that occurs during a fever (febrile seizure). About a third of the children who have one febrile seizure will have another one, most commonly within the next 12 months.
A febrile seizure may involve loss of consciousness, shaking of limbs on both sides of the body, eyes rolling back or body stiffness. Although alarming for parents, the vast majority of febrile seizures cause no lasting effects.
If a seizure occurs:
•Lay your child on the side or stomach on the floor or ground
•Remove any sharp objects that are near your child
•Loosen tight clothing
You may be able to prevent fevers by reducing exposure to infectious diseases. Here are some tips that can help:
•Get vaccinated as recommended for infectious diseases, such as influenza and COVID-19.
•Follow public health guidelines for wearing masks and social distancing.
•Wash your hands often and teach your children to do the same, especially before eating, after using the toilet, after spending time in a crowd or around someone who's sick, after petting animals, and during travel on public transportation.
•Show your children how to wash their hands thoroughly, covering both the front and back of each hand with soap and rinsing completely under running water.
•Carry hand sanitizer with you for times when you don't have access to soap and water.
•Mayo Clinic Minute: What to do and not do when your child has a viral fever
•Mayo Clinic Minute: Acetaminophen aids with fever, pain
•Fever treatment: Quick guide to treating a fever
•Thermometers: Understand the options
Fever is a common sign of infection or other conditions that affect the immune system. Learn how to measure, treat, and prevent fever in adults, and when to seek medical help.
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Learn what a fever is, how to measure it, and when to see a doctor. Find out how to treat fever at home and prevent complications such as dehydration and febrile convulsions.
- A fever is when your body temperature is higher than normal. Having a fever can also be called ‘having a temperature’. A normal temperature is arou...
- Adults with a fever should see a doctor straight away if they have symptoms such as: a severe headache sensitivity to bright light an unusual skin...
- If you have a fever, you will have a high temperature. A high temperature is usually considered to be above 38°C. You may also have other symptoms,...
- Fever is a part of your immune system response. If you have a fever, it is a sign that your body is working hard to get well. A high temperature is...
- Fever is diagnosed by taking your temperature. You can do this yourself. You probably have a fever if your temperature is 38°C or higher. A doctor...
- If you have a high temperature there are several things you can do to help manage your condition. Keep hydrated It's important to stay well hydrate...
- If your fever doesn’t go away, or you experience other symptoms mentioned above, you can prevent further complications by seeking medical attention...
Jan 18, 2024 · A fever is a body temperature of 38°C (100.4°F) or higher, usually caused by an infection or illness. Learn how to measure fever, when to treat it and when to call a doctor for adults and children.
Jul 2, 2024 · Learn what is the normal body temperature for babies, kids, adults, and older adults, and how to measure it accurately. Find out what factors can affect your temperature and when to seek medical help for a fever.
Jun 20, 2024 · Learn how to measure your body temperature and when to call a doctor. Find out why the average temperature is lower than 98.6 F and how it affects COVID-19 diagnosis.