Table of ContentsView AllTable of ContentsNormal TemperatureFeverAt-HomeSchool or WorkWhen to See a ProviderCauses of Fever
Table of ContentsView All
View All
Table of Contents
Normal Temperature
Fever
At-Home
School or Work
When to See a Provider
Causes of Fever
Fever is an elevation in the body’s temperature. It’s not a disease but rather a sign or response to something occurring within the body, most commonly an infection. Noninfectious conditions or scenarios like inflammatory diseases or medication reactions can also cause a fever.
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What Is Considered a Normal Body Temperature?
To understand fever, it’s important first to understand what a normal body temperature is.
Normal Body Temperature Ranges
There is no formal definition for a normal body temperature, although general ranges exist.
Factors affecting body temperature include age, measurement site (e.g., mouth vs. rectum vs. underarm), and time of day. Body temperature is naturally at its lowest in the early morning and highest in the late afternoon.
In mostbabies and children, the normal body temperature range is between 97.7 F (36.5 C) and 99.5 F (37.5 C).Their slightly higher body temperature is attributed to their greater total surface area in relation to their body weight and higher metabolisms.
Measurement SitesSites on the body for measuring temperature include:Mouth (oral): The tip of thethermometeris placed under the tongue and facing toward the back of the mouth.Rectum(rectal): A small amount of petroleum jelly is applied to the end of the thermometer, which is then placed one-half inch inside the anal canal. Rectal thermometers provide the best reading for babies under 3 months.Armpit (axillary): The tip of the thermometer is placed on the skin in the armpit. This measurement method is invariably lower than the rectal or mouth temperature.Ear (tympanic): The top of the ear is pulled back, and an infrared scanning device is gently placed in the ear canal. The device uses heat from the eardrum and surrounding tissue to detect body temperature.Forehead (temporal): An infrared scanning device is slid or aimed across the forehead. It uses heat waves radiating off the forehead (temporal) artery to detect body temperature.
Measurement Sites
Sites on the body for measuring temperature include:Mouth (oral): The tip of thethermometeris placed under the tongue and facing toward the back of the mouth.Rectum(rectal): A small amount of petroleum jelly is applied to the end of the thermometer, which is then placed one-half inch inside the anal canal. Rectal thermometers provide the best reading for babies under 3 months.Armpit (axillary): The tip of the thermometer is placed on the skin in the armpit. This measurement method is invariably lower than the rectal or mouth temperature.Ear (tympanic): The top of the ear is pulled back, and an infrared scanning device is gently placed in the ear canal. The device uses heat from the eardrum and surrounding tissue to detect body temperature.Forehead (temporal): An infrared scanning device is slid or aimed across the forehead. It uses heat waves radiating off the forehead (temporal) artery to detect body temperature.
Sites on the body for measuring temperature include:
How to Use a Thermometer to Check for Fever
What’s Considered a Fever?
Thehypothalamusis a small gland in the brain that controls the body’s temperature, like a thermostat. Fever is an increase in body temperature that occurs when the hypothalamus’s set point is shifted upwards in response to inflammation or infection.
Generally accepted ranges include the following:
Rectal temperatures should be taken for children under 4 years old, as they provide the most accurate reading.Oral temperatures are generally acceptable for children around 4 or 5 years old. Forehead thermometers may be used for all ages. Axillary and tympanic temperatures are not recommended, as they are unreliable in young children.
Low-Grade Fever Temperature Range
A low-grade fever generally indicates a body temperature that is slightly above normal. There is no formally defined range, but one research article categorized it as between 99.1 F and 100.4 F.
High Fever Temperature Range
A high fever indicates a body temperature that is possibly serious or dangerous.
Again, there is no formal definition, but typically, a high fever is 102.2 F or greater inbabies 3 months and older and younger children.
A high fever inolder children and adultsis a temperature of 102.4 F or greater.
Fevers above 105.8 F are termed “hyperpyrexia” and can be seen with brain dysfunction, severe infections,orbrain bleeds.
Causes include:
When Is a Fever Too High?
How to Break a Fever at Home
Many fevers can be safely treated at home with fluids and rest, assuming no symptoms or signs of a serious illness are present.
Antipyretic Drugs
Sometimes, fever-reducing medicines—calledantipyreticagents—are used to ease discomfort, especially if the fever is high or other symptoms related to the fever are present. These can include malaise (general feeling of being unwell), headache, and muscle aches.
Antipyretic agents are also often indicated in individuals with underlying heart or lung diseases, as fever can increase heart and breathing rates.
Tylenol (acetaminophen)and thenonsteroidal anti-inflammatory drug(NSAID)ibuprofen, sold under the brand names Advil or Motrin, are commonly used antipyretics.
Take PrecautionsTake an antipyretic (or give your child) only under the guidance of a healthcare provider, as they do carry risks.
Take Precautions
Take an antipyretic (or give your child) only under the guidance of a healthcare provider, as they do carry risks.
Taking too much Tylenol can cause liver injury and damage.Likewise, too much ibuprofen and other NSAIDs can cause stomach bleeding and may need to be avoided in individuals with heart or kidney disease, high blood pressure (hypertension), or bleeding problems.
This is why it is important to read the medication label carefully when giving these medications. Information on the label can help you determine the correctdose and frequencybased on your child’s weight.
Also, the NSAIDaspirinshould never be used in kids under 19, as it’s associated withReye’s syndrome., a life-threatening condition.
An antipyretic is often unnecessary in a child older than 3 months who has a rectal temperature less than 102 F (38.9 C), seems well, and is behaving like their usual selves.
Cooling Therapies
Cooling therapies—such as cooling blankets or cool-water sponge baths—can help reduce fever in adults with high fevers, but only when used concurrently with an antipyretic.This is because physical cooling of the body causes blood vessels in the skin to narrow, decreasing the body’s ability to lose heat.
Cooling therapies are not recommended in babies or children with a fever-related illness.
School and Work With a Fever
To prevent the spread of infection, a child or adult should be fever-free for 24 hours without the use of fever-reducing medications) and feel and appear well before returning to school, work, or other activities.
Fever Symptoms That Warrant Medical Attention
In many instances, seeing a healthcare provider or going to the emergency room is unnecessary for a fever, as the cause is often a viral infection that needs to run its course, typically three to five days.
That said, certain factors, such as an ill-appearing child or adult, underlying medical conditions, or worrisome symptoms, warrant medical attention.
Babies and Children
According to the American Academy of Pediatricsand experts from UpToDate,seek medical attention in the following scenarios:
In addition, infants and children with a fever and any of the following symptoms also require immediate medical attention:
Understanding Fever in Children
Adults
If you are an adult and have a fever, seek medical attention right away if you:
Do Not Hesitate to Get HelpIf you (or your child) have a fever and are experiencing unusual or worrisome symptoms or have that gut instinct that something is wrong, don’t hesitate to contact a healthcare provider or go to your nearest emergency room.
Do Not Hesitate to Get Help
If you (or your child) have a fever and are experiencing unusual or worrisome symptoms or have that gut instinct that something is wrong, don’t hesitate to contact a healthcare provider or go to your nearest emergency room.
There are multiple potential causes of fever.
Viral Infections are the most common cause. Examples include:
Other causes include bacterial infections such as:
Summary
Fever is an elevation of the body’s temperature and occurs when the set-point of the brain’s thermostat shifts upwards.
Fever is a response to something in the body, usually a viral infection like the flu or COVID-19. Bacterial infections, such as urinary tract or skin infections, can also trigger fevers, as can noninfectious causes like autoimmune diseases or drug reactions.
No formal or standard definition exists for fever, as it can vary depending on age, time of day, and where it’s measured on the body (e.g., mouth, rectal, ear, underarm, or forehead).
Most cases of fever are due to viral infections. They can be managed at home with fluids, rest, and, sometimes, a fever-reducing medication like Tylenol or ibuprofen (under the guidance of a healthcare provider)
Likewise, the presence of worrisome symptoms, in addition to the fever, like trouble breathing or signs of dehydration, requires immediate medical attention. While many fevers can be managed safely at home, contact a healthcare provider if you have questions or concerns or if your gut instinct is kicking in.
22 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Bush LM.Fever. Merck Manual Professional Version.Speaker SL, Pfoh ER, Pappas MA, Hu B, Rothberg MB.Oral temperature of noninfected hospitalized patients.JAMA. 2021;325(18):1899-1901. doi:10.1001/jama.2021.1541InformedHealth.org.Overview: fever in children.American Academy of Pediatrics.Thermometers 101: how to check temperature during COVID-19 pandemicAmerican Academy of Pediatrics.Fever without fear: information for parents.Ward MA.Fever in infants and children. In:UpToDate, Edwards MS (Ed), UpToDate, Waltham, MA.American Academy of Pediatrics.How to take your child’s temperature.Islam MA, Kundu S, Alam SS, Hossan T, Kamal MA, Hassan R.Prevalence and characteristics of fever in adult and paediatric patients with coronavirus disease 2019 (COVID-19): a systematic review and meta-analysis of 17515 patients.PLoS One. 2021;16(4):e0249788. doi:10.1371/journal.pone.0249788KidsHealth.Fever (high temperature) in kids.Suwanwongse K, Shabarek N.Hyperpyrexia in patients with COVID-19.J Med Virol. 2020;92(11):2857-2862. doi:10.1002/jmv.26154Samudra N, Figueroa S.Intractable central hyperthermia in the setting of brainstem hemorrhage.Ther Hypothermia Temp Manag. 2016;6(2):98-101. doi:10.1089/ther.2016.0004Harvard Health Publishing.Heat stroke (hyperthermia).Bach V, Libert JP.Hyperthermia and Heat Stress as Risk Factors for Sudden Infant Death Syndrome: A Narrative Review.Front Pediatr. 2022 Apr 15;10:816136. doi:10.3389/fped.2022.816136Bush LM.Fever in adults. Merck Manual Consumer Version.National Institute of Diabetes and Digestive and Kidney Diseases.Clinical and research information on drug-induced liver injury: acetaminophen.DailyMed.Label: ibuprofen tablet.Barbi E, Marzuillo P, Neri E, Naviglio S, Krauss BS.Fever in children: pearls and pitfalls.Children (Basel). 2017;4(9):81. doi:10.3390/children4090081Ward MA.Patient education: fever in children (beyond the basics). In:UpToDate, Edwards MS (Ed), UpToDate, Waltham, MADinarello CA, Porat R.Pathophysiology and treatment of fever in adults. In:UpToDate, Spelman D (Ed), UpToDate, Waltham, MA.Centers for Disease Control and Prevention.Preventing the spread of respiratory viruses when you’re sick.El-Radhi AS.Fever in common infectious diseases.Clinical Manual of Fever in Children. 2019:85–140. doi:10.1007/978-3-319-92336-9_5Steele GM, Franco-Paredes C, Chastain DB.Noninfectious causes of fever in adults.Nurse Pract.2018;43(4):38-44. doi:10.1097/01.NPR.0000531067.65817.7d
22 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Bush LM.Fever. Merck Manual Professional Version.Speaker SL, Pfoh ER, Pappas MA, Hu B, Rothberg MB.Oral temperature of noninfected hospitalized patients.JAMA. 2021;325(18):1899-1901. doi:10.1001/jama.2021.1541InformedHealth.org.Overview: fever in children.American Academy of Pediatrics.Thermometers 101: how to check temperature during COVID-19 pandemicAmerican Academy of Pediatrics.Fever without fear: information for parents.Ward MA.Fever in infants and children. In:UpToDate, Edwards MS (Ed), UpToDate, Waltham, MA.American Academy of Pediatrics.How to take your child’s temperature.Islam MA, Kundu S, Alam SS, Hossan T, Kamal MA, Hassan R.Prevalence and characteristics of fever in adult and paediatric patients with coronavirus disease 2019 (COVID-19): a systematic review and meta-analysis of 17515 patients.PLoS One. 2021;16(4):e0249788. doi:10.1371/journal.pone.0249788KidsHealth.Fever (high temperature) in kids.Suwanwongse K, Shabarek N.Hyperpyrexia in patients with COVID-19.J Med Virol. 2020;92(11):2857-2862. doi:10.1002/jmv.26154Samudra N, Figueroa S.Intractable central hyperthermia in the setting of brainstem hemorrhage.Ther Hypothermia Temp Manag. 2016;6(2):98-101. doi:10.1089/ther.2016.0004Harvard Health Publishing.Heat stroke (hyperthermia).Bach V, Libert JP.Hyperthermia and Heat Stress as Risk Factors for Sudden Infant Death Syndrome: A Narrative Review.Front Pediatr. 2022 Apr 15;10:816136. doi:10.3389/fped.2022.816136Bush LM.Fever in adults. Merck Manual Consumer Version.National Institute of Diabetes and Digestive and Kidney Diseases.Clinical and research information on drug-induced liver injury: acetaminophen.DailyMed.Label: ibuprofen tablet.Barbi E, Marzuillo P, Neri E, Naviglio S, Krauss BS.Fever in children: pearls and pitfalls.Children (Basel). 2017;4(9):81. doi:10.3390/children4090081Ward MA.Patient education: fever in children (beyond the basics). In:UpToDate, Edwards MS (Ed), UpToDate, Waltham, MADinarello CA, Porat R.Pathophysiology and treatment of fever in adults. In:UpToDate, Spelman D (Ed), UpToDate, Waltham, MA.Centers for Disease Control and Prevention.Preventing the spread of respiratory viruses when you’re sick.El-Radhi AS.Fever in common infectious diseases.Clinical Manual of Fever in Children. 2019:85–140. doi:10.1007/978-3-319-92336-9_5Steele GM, Franco-Paredes C, Chastain DB.Noninfectious causes of fever in adults.Nurse Pract.2018;43(4):38-44. doi:10.1097/01.NPR.0000531067.65817.7d
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Bush LM.Fever. Merck Manual Professional Version.Speaker SL, Pfoh ER, Pappas MA, Hu B, Rothberg MB.Oral temperature of noninfected hospitalized patients.JAMA. 2021;325(18):1899-1901. doi:10.1001/jama.2021.1541InformedHealth.org.Overview: fever in children.American Academy of Pediatrics.Thermometers 101: how to check temperature during COVID-19 pandemicAmerican Academy of Pediatrics.Fever without fear: information for parents.Ward MA.Fever in infants and children. In:UpToDate, Edwards MS (Ed), UpToDate, Waltham, MA.American Academy of Pediatrics.How to take your child’s temperature.Islam MA, Kundu S, Alam SS, Hossan T, Kamal MA, Hassan R.Prevalence and characteristics of fever in adult and paediatric patients with coronavirus disease 2019 (COVID-19): a systematic review and meta-analysis of 17515 patients.PLoS One. 2021;16(4):e0249788. doi:10.1371/journal.pone.0249788KidsHealth.Fever (high temperature) in kids.Suwanwongse K, Shabarek N.Hyperpyrexia in patients with COVID-19.J Med Virol. 2020;92(11):2857-2862. doi:10.1002/jmv.26154Samudra N, Figueroa S.Intractable central hyperthermia in the setting of brainstem hemorrhage.Ther Hypothermia Temp Manag. 2016;6(2):98-101. doi:10.1089/ther.2016.0004Harvard Health Publishing.Heat stroke (hyperthermia).Bach V, Libert JP.Hyperthermia and Heat Stress as Risk Factors for Sudden Infant Death Syndrome: A Narrative Review.Front Pediatr. 2022 Apr 15;10:816136. doi:10.3389/fped.2022.816136Bush LM.Fever in adults. Merck Manual Consumer Version.National Institute of Diabetes and Digestive and Kidney Diseases.Clinical and research information on drug-induced liver injury: acetaminophen.DailyMed.Label: ibuprofen tablet.Barbi E, Marzuillo P, Neri E, Naviglio S, Krauss BS.Fever in children: pearls and pitfalls.Children (Basel). 2017;4(9):81. doi:10.3390/children4090081Ward MA.Patient education: fever in children (beyond the basics). In:UpToDate, Edwards MS (Ed), UpToDate, Waltham, MADinarello CA, Porat R.Pathophysiology and treatment of fever in adults. In:UpToDate, Spelman D (Ed), UpToDate, Waltham, MA.Centers for Disease Control and Prevention.Preventing the spread of respiratory viruses when you’re sick.El-Radhi AS.Fever in common infectious diseases.Clinical Manual of Fever in Children. 2019:85–140. doi:10.1007/978-3-319-92336-9_5Steele GM, Franco-Paredes C, Chastain DB.Noninfectious causes of fever in adults.Nurse Pract.2018;43(4):38-44. doi:10.1097/01.NPR.0000531067.65817.7d
Bush LM.Fever. Merck Manual Professional Version.
Speaker SL, Pfoh ER, Pappas MA, Hu B, Rothberg MB.Oral temperature of noninfected hospitalized patients.JAMA. 2021;325(18):1899-1901. doi:10.1001/jama.2021.1541
InformedHealth.org.Overview: fever in children.
American Academy of Pediatrics.Thermometers 101: how to check temperature during COVID-19 pandemic
American Academy of Pediatrics.Fever without fear: information for parents.
Ward MA.Fever in infants and children. In:UpToDate, Edwards MS (Ed), UpToDate, Waltham, MA.
American Academy of Pediatrics.How to take your child’s temperature.
Islam MA, Kundu S, Alam SS, Hossan T, Kamal MA, Hassan R.Prevalence and characteristics of fever in adult and paediatric patients with coronavirus disease 2019 (COVID-19): a systematic review and meta-analysis of 17515 patients.PLoS One. 2021;16(4):e0249788. doi:10.1371/journal.pone.0249788
KidsHealth.Fever (high temperature) in kids.
Suwanwongse K, Shabarek N.Hyperpyrexia in patients with COVID-19.J Med Virol. 2020;92(11):2857-2862. doi:10.1002/jmv.26154
Samudra N, Figueroa S.Intractable central hyperthermia in the setting of brainstem hemorrhage.Ther Hypothermia Temp Manag. 2016;6(2):98-101. doi:10.1089/ther.2016.0004
Harvard Health Publishing.Heat stroke (hyperthermia).
Bach V, Libert JP.Hyperthermia and Heat Stress as Risk Factors for Sudden Infant Death Syndrome: A Narrative Review.Front Pediatr. 2022 Apr 15;10:816136. doi:10.3389/fped.2022.816136
Bush LM.Fever in adults. Merck Manual Consumer Version.
National Institute of Diabetes and Digestive and Kidney Diseases.Clinical and research information on drug-induced liver injury: acetaminophen.
DailyMed.Label: ibuprofen tablet.
Barbi E, Marzuillo P, Neri E, Naviglio S, Krauss BS.Fever in children: pearls and pitfalls.Children (Basel). 2017;4(9):81. doi:10.3390/children4090081
Ward MA.Patient education: fever in children (beyond the basics). In:UpToDate, Edwards MS (Ed), UpToDate, Waltham, MA
Dinarello CA, Porat R.Pathophysiology and treatment of fever in adults. In:UpToDate, Spelman D (Ed), UpToDate, Waltham, MA.
Centers for Disease Control and Prevention.Preventing the spread of respiratory viruses when you’re sick.
El-Radhi AS.Fever in common infectious diseases.Clinical Manual of Fever in Children. 2019:85–140. doi:10.1007/978-3-319-92336-9_5
Steele GM, Franco-Paredes C, Chastain DB.Noninfectious causes of fever in adults.Nurse Pract.2018;43(4):38-44. doi:10.1097/01.NPR.0000531067.65817.7d
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