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[Skip to main content](https://ufhealth.org/conditions-and-treatments/fever#maincontent) [(352) 733-0111](tel:+13527330111) [MyUFHealth](https://mychart.shands.org/mychartprd/Authentication/Login) [UF Health Home](https://ufhealth.org/) Search Close Menu - [Find a Doctor](https://ufhealth.org/doctors) - [Conditions & Treatments](https://ufhealth.org/conditions-and-treatments) - [Locations](https://ufhealth.org/locations) - [Patients & Visitors](https://ufhealth.org/patients-and-visitors) - [Clinical Trials](https://ufhealth.org/clinical-trials) - [Community](https://ufhealth.org/community) - [Billing](https://ufhealth.org/billing-insurance-and-costs) - [Insurance](https://ufhealth.org/billing-insurance-and-costs/insurance) - [Events](https://ufhealth.org/events) - [Make a gift](https://ufhealth.org/giving) - [Careers](https://careers.ufhealth.org/) - [Volunteer](https://ufhealth.org/volunteering) - [Education](https://ufhealth.org/education) - [Research](https://ufhealth.org/research) - [About](https://ufhealth.org/about-uf-health) [(352) 733-0111](tel:+13527330111) [MyUFHealth](https://mychart.shands.org/mychartprd/Authentication/Login) Close [Conditions and Treatments](https://ufhealth.org/conditions-and-treatments) # Fever ## Fever Menu Open Menu Fever Menu Close ## Fever Menu Collapse Fever Menu - [Overview](https://ufhealth.org/conditions-and-treatments/fever) - [Locations](https://ufhealth.org/conditions-and-treatments/fever/locations) - [Stories and news](https://ufhealth.org/conditions-and-treatments/fever/stories) ## On this page Collapse navigation ## Definition Fever is the temporary increase in the body's temperature in response to a disease or illness. A child has a fever when the temperature is at or above one of these levels: - 100\.4°F (38°C) measured in the bottom (rectally) - 99\.5°F (37.5°C) measured in the mouth (orally) - 99°F (37.2°C) measured under the arm (axillary) An adult probably has a fever when the temperature is above 99°F to 99.5°F (37.2°C to 37.5°C), depending on the time of day. ## Alternative Names Elevated temperature; Hyperthermia; Pyrexia; Febrile ## Considerations Normal body temperature may change during any given day. It is usually highest in the evening. Other factors that may affect body temperature are: - A woman's menstrual cycle. In the second part of this cycle, her temperature may go up by 1 degree Fahrenheit or more. - Physical activity, strong emotion, eating, heavy clothing, medicines, high room temperature, and high humidity can all increase body temperature. Fever is an important part of the body's defense against infection. Most bacteria and viruses that cause infections in people thrive best at 98.6°F (37°C). Many infants and children develop high fevers with mild viral illnesses. Although a fever signals that a battle might be going on in the body, the fever is fighting for, not against the person. Brain damage from a fever generally will not occur unless the fever is over 107.6°F (42°C). Untreated fevers caused by infection will seldom go over 105°F (40.6°C) unless the child is overdressed or in a hot place. [Febrile seizures](https://ufhealth.org/adam/1/000980) do occur in some children. Most febrile seizures are over quickly and do not mean your child has epilepsy. These seizures also do not cause any permanent harm. Unexplained fevers that continue for days or weeks are called fevers of undetermined origin (FUO). ## Causes Almost any infection can cause a fever, including: - Bone infections ([osteomyelitis](https://ufhealth.org/adam/1/000437)), [appendicitis](https://ufhealth.org/adam/1/000256), skin infections or [cellulitis](https://ufhealth.org/adam/1/000855), and [meningitis](https://ufhealth.org/adam/1/000680) - Respiratory infections such as [colds](https://ufhealth.org/adam/1/000678) or [flu](https://ufhealth.org/adam/1/000080)\-like illnesses, [sore throats](https://ufhealth.org/adam/1/000655), [ear infections](https://ufhealth.org/adam/1/001336), [sinus infections](https://ufhealth.org/adam/1/000647), [mononucleosis](https://ufhealth.org/adam/1/000591), [bronchitis](https://ufhealth.org/adam/1/001087), [pneumonia](https://ufhealth.org/adam/1/000145), and [tuberculosis](https://ufhealth.org/adam/1/000077) - [Urinary tract infections](https://ufhealth.org/adam/1/000521) - [Viral gastroenteritis](https://ufhealth.org/adam/1/000252) and [bacterial gastroenteritis](https://ufhealth.org/adam/1/000254) Children and adults may have a low-grade fever for 1 or 2 days after some [immunizations](https://ufhealth.org/adam/1/002024). [Teething](https://ufhealth.org/adam/1/002045) may cause a slight increase in a child's temperature, but not higher than 100°F (37.8°C). Autoimmune or inflammatory disorders may also cause fevers. Some examples are: - [Arthritis](https://ufhealth.org/adam/1/001243) or connective tissue illnesses such as [rheumatoid arthritis](https://ufhealth.org/adam/1/000431) and [systemic lupus erythematosus](https://ufhealth.org/adam/1/000435) - [Ulcerative colitis](https://ufhealth.org/adam/1/000250) and [Crohn disease](https://ufhealth.org/adam/1/000249) - [Vasculitis](https://ufhealth.org/adam/1/000874) or [periarteritis nodosa](https://ufhealth.org/adam/1/001438) The first symptom of a cancer may be a fever. This is particularly true of [Hodgkin disease](https://ufhealth.org/adam/1/000580), [non-Hodgkin lymphoma](https://ufhealth.org/adam/1/000581), and [leukemia](https://ufhealth.org/adam/1/001299). Other possible causes of fever include: - [Blood clots](https://ufhealth.org/adam/1/001124) or [thrombophlebitis](https://ufhealth.org/adam/1/001108) - Medicines, such as some antibiotics, antihistamines, and seizure medicines ## Home Care A simple cold or other viral infection can sometimes cause a high fever (102°F to 104°F or 38.9°C to 40°C). This does not mean you or your child has a serious problem. Some serious infections don't cause a fever or can cause a very low body temperature, most often in infants. If the fever is mild and you have no other problems, you do not need treatment. Drink fluids and rest. The illness is probably not serious if your child: - Is still interested in playing - Is eating and drinking well - Is alert and smiling at you - Has a normal skin color - Looks well when their temperature comes down Take steps to lower a fever if you or your child is uncomfortable, vomiting, dried out (dehydrated), or not sleeping well. Remember, the goal is to lower, not eliminate, the fever. When trying to lower a fever: - Do not bundle up someone who has chills. - Remove excess clothing or blankets. The room should be comfortable, not too hot or cool. Try one layer of lightweight clothing, and one lightweight blanket for sleep. If the room is hot or stuffy, a fan may help. - A lukewarm bath or sponge bath may help cool someone with a fever. This is effective after medicine is given -- otherwise the temperature might bounce right back up. - Do not use cold baths, ice, or alcohol rubs. These cool the skin, but often make the situation worse by causing shivering, which raises the core body temperature. Here are some guidelines for taking medicine to lower a fever: - Acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) help reduce fever in children and adults. Sometimes health care providers advise you to use both types of medicine. - Take acetaminophen every 4 to 6 hours. It works by turning down the brain's thermostat. - Take ibuprofen every 6 to 8 hours. Do not use ibuprofen in children 6 months or younger. - Aspirin is very effective for treating fever in adults. Do not give aspirin to a child unless your child's provider tells you to. - Know how much you or your child weighs. Then check the instructions on the package to find the correct dose. - In children 3 months or younger, call your child's provider first before giving medicines. Eating and drinking: - Everyone, particularly children, should drink plenty of fluids. Water, ice pops, soup, and gelatin are all good choices. - In younger children do not give too much fruit juice or apple juice, and do not give sports drinks. - Although eating is fine, do not force foods. ## When to Contact a Medical Professional Contact a provider right away if your child: - Is 3 months or younger and has a rectal temperature of 100.4°F (38°C) or higher - Is 3 to 12 months old and has a fever of 102.2°F (39°C) or higher - Is 2 years or younger and has a fever that lasts longer than 24 to 48 hours - Is older and has a fever for longer than 48 to 72 hours - Has a fever of 105°F (40.5°C) or higher, unless it comes down readily with treatment and the person is comfortable - Has other symptoms that suggest an illness may need to be treated, such as a sore throat, [earache](https://ufhealth.org/adam/1/003046), or [cough](https://ufhealth.org/adam/1/003072) - Has had fevers come and go for up to a week or more, even if these fevers are not very high - Has a serious medical illness, such as a heart problem, sickle cell anemia, diabetes, or cystic fibrosis - Recently had an immunization - Has a new rash or bruises - Has pain with urination - Has a weakened immune system (because of long-term \[chronic\] steroid therapy, a bone marrow or organ transplant, spleen removal, HIV/AIDS, or cancer treatment) - Has recently traveled to another country Contact your provider right away if you are an adult and you: - Have a fever of 105°F (40.5°C) or higher, unless it comes down readily with treatment and you are comfortable - Have a fever that stays at or keeps rising above 103°F (39.4°C) - Have a fever for longer than 48 to 72 hours - Have had fevers come and go for up to a week or more, even if they are not very high - Have a serious medical illness, such as a [heart problem](https://ufhealth.org/adam/60/000775), [sickle cell anemia](https://ufhealth.org/adam/1/000527), [diabetes](https://ufhealth.org/adam/1/001214), [cystic fibrosis](https://ufhealth.org/adam/1/000107), [COPD](https://ufhealth.org/adam/1/000091), or other long-term (chronic) lung problems - Have a new rash or bruises - Have pain with urination - Have a weakened immune system (from chronic steroid therapy, a bone marrow or organ transplant, spleen removal, [HIV/AIDS](https://ufhealth.org/adam/1/000594), or cancer treatment) - Have recently traveled to another country Call 911 or the local emergency number if you or your child has a fever and: - Is crying and cannot be calmed (children) - Cannot be awakened easily or at all - Seems confused - Cannot walk - Has difficulty breathing, even after the nose is cleared - Has blue lips, tongue, or nails - Has a very bad headache - Has a stiff neck - Refuses to move an arm or leg (children) - Has a seizure ## What to Expect at Your Office Visit Your provider will perform a physical exam. This may include a detailed examination of the skin, eyes, ears, nose, throat, neck, chest, and abdomen to look for the cause of the fever. Treatment depends on the duration and cause of the fever, as well as other symptoms. The following tests may be performed: - Blood tests, such as a [CBC](https://ufhealth.org/adam/1/003642) or [white blood cell differential](https://ufhealth.org/adam/1/003657) - [Urinalysis](https://ufhealth.org/adam/1/003579) - [X-ray of the chest](https://ufhealth.org/adam/1/003804) ## Gallery [ Fever is an important part of the body's defense against infection. Most bacteria and viruses that cause infections in humans thrive best at 98.6 degrees F (37 degrees C). Raising the body temperature a few degrees can help the body fight the infection. In addition, a fever activates the body's immune system to make more white blood cells, antibodies, and other infection-fighting agents.](https://ufhealth.org/assets/adam/19700.jpg) [ A thermometer is a useful aid used to measure body temperature. A thermometer is usually filled with mercury. Mercury in the tube rises when expanded by an increase in body temperature.](https://ufhealth.org/assets/adam/9961.jpg) ## References Leggett JE. Approach to fever or suspected infection in the normal host. In: Goldman L, Schafer AI, eds. *Goldman-Cecil Medicine*. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 264. Nield LS, Kamat D. Fever. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. *Nelson Textbook of Pediatrics*. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 201. Last reviewed July 31, 2024 by Charles I. Schwartz, MD, FAAP, Clinical Assistant Professor of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, General Pediatrician at PennCare for Kids, Phoenixville, PA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.. ## Related specialties - [Family Medicine](https://ufhealth.org/specialties/family-medicine) - [Pediatrics](https://ufhealth.org/specialties/pediatrics) ## Aftercare and more - [Colds and the Flu - What to Ask Your Doctor - Adult](https://ufhealth.org/care-sheets/colds-and-the-flu-what-to-ask-your-doctor-adult) - [Colds and the Flu - What to Ask Your Doctor - Child](https://ufhealth.org/care-sheets/colds-and-the-flu-what-to-ask-your-doctor-child) - [Febrile Seizures - What to Ask Your Doctor](https://ufhealth.org/care-sheets/febrile-seizures-what-to-ask-your-doctor) - [When Your Baby or Infant Has a Fever](https://ufhealth.org/care-sheets/when-your-baby-or-infant-has-a-fever) ## Our locations ## News and patient stories: Fever # [Scientists say these two viruses may become the next public health threats](https://ufhealth.org/news/2026/scientists-say-these-two-viruses-may-become-the-next-public-health-threats) January 28, 2026 GAINESVILLE, Fla. — Two emerging pathogens with animal origins — influenza D virus and canine coronavirus — have so far been quietly flying under the radar,… College of Public Health and Health Professions, Emerging Pathogens Institute, +1 more  # [Heart of a Nurse, Love of a Mother: Taylor Smith, RN, Brings Compassion to Both Worlds](https://ufhealth.org/stories/2025/heart-of-a-nurse-love-of-a-mother-taylor-smith-rn-brings-compassion-to-both-worlds) As both a UF Health Shands team member and the mother of a patient, Taylor Smith, RN, sees UF Health as more than a workplace — it’s part of her family’s…  [More Fever stories](https://ufhealth.org/conditions-and-treatments/fever/stories) ## Latest podcast episodes # [Have a mild fever? Hold off on medication](https://podcasts.ufhealth.org/have-a-mild-fever-hold-off-on-medication/) For some people, reaching into the medicine cabinet to treat a mild fever is a reflexive action. It might be a good idea to hold off on that. New research suggests that it could be better to let a... # [Fever during pregnancy increases risk of autism](https://podcasts.ufhealth.org/fever-during-pregnancy-increases-risk-of-autism/) According to the U.S. Centers for Disease Control and Prevention, about one in 80 children in America are now diagnosed with some form of autism every year. As the incidence of this developmental... # [Fevers could be beneficial](https://podcasts.ufhealth.org/fevers-could-be-beneficial/) Feeling a little hot? It could be a fever coming on. But before you run for the Tylenol, hear this: New research has found that a mild fever could actually be good for you. According to research... [Listen to more Health in a Heartbeat episodes](https://podcasts.ufhealth.org/category/health-in-a-heartbeat/) [University of Florida Health ![]()](https://ufhealth.org/) [University of Florida ![]()](https://ufl.edu/) [(352) 733-0111](tel:+13527330111) [MyUFHealth](https://mychart.shands.org/mychartprd/Authentication/Login) [Make a Gift](https://ufhealth.org/giving) ## Patients & Visitors - [About UF Health](https://ufhealth.org/about-uf-health) - [Locations](https://ufhealth.org/locations) - [Medical Records](https://ufhealth.org/medical-records) - [Billing, Costs & Insurances](https://ufhealth.org/billing-insurance-and-costs) - [Visiting UF Health](https://ufhealth.org/patients-and-visitors) ## Health Professionals - [Referrals, Consults & Transfers](https://ufhealth.org/physician-referrals) - [Continuing Education](https://ufhealth.org/health-professionals/continuing-education) - [Credentialing](https://professionals.ufhealth.org/credentialing-and-provider-enrollment) - [Labs](https://ufhealth.org/specialties/pathology-immunology-and-laboratory-medicine) ## Research & Education - [Colleges](https://ufhealth.org/education) - [Research](https://ufhealth.org/research) - [Centers & Institutes](https://ufhealth.org/research/centers-and-institutes) - [Libraries](https://library.health.ufl.edu/) - [Research Support](https://ufhealth.org/research/for-researchers) ## Get Involved - [Careers](https://careers.ufhealth.org/) - [Volunteer](https://ufhealth.org/volunteering) ## Employees - [UF Health Bridge](https://bridge.ufhealth.org/) - [St Johns Intranet](https://flagler.hospitalportal.net/Flagler/) - [VPN](https://ufhealth.org/virtual-private-network-vpn) ## News & Events [UF Health Stories](https://ufhealth.org/stories) [Newsroom](https://ufhealth.org/news) [Events](https://ufhealth.org/events) ## Connect with UF Health [Facebook](https://facebook.com/UFHealth) [Twitter](https://www.twitter.com/ufhealth) [Instagram](https://www.instagr.am/ufhealth) [YouTube](https://www.youtube.com/channel/UCT4ayrjE0xcfZ8fQHYbfiTA) [LinkedIn](https://www.linkedin.com/company/uf-health) [Report a site issue](https://ufhealth.org/report-a-site-issue?title=Fever&url=https://ufhealth.org/conditions-and-treatments/fever) [Disclaimer & Permitted Use](https://ufhealth.org/disclaimer-and-permitted-use) [Nondiscrimination and Accessibility](https://ufhealth.org/accessibility-and-nondiscrimination%20) [Security and Privacy](https://ufhealth.org/privacy-and-security-policies) [Price Transparency](https://ufhealth.org/price-transparency) [This site uses Google Analytics](https://ufhealth.org/privacy-and-security-policies/uf-health-website-privacy-policy#google-analytics) Updated: February 5, 2026 © 2026 UF Health

## Definition Fever is the temporary increase in the body's temperature in response to a disease or illness. A child has a fever when the temperature is at or above one of these levels: - 100\.4°F (38°C) measured in the bottom (rectally) - 99\.5°F (37.5°C) measured in the mouth (orally) - 99°F (37.2°C) measured under the arm (axillary) An adult probably has a fever when the temperature is above 99°F to 99.5°F (37.2°C to 37.5°C), depending on the time of day. ## Alternative Names Elevated temperature; Hyperthermia; Pyrexia; Febrile ## Considerations Normal body temperature may change during any given day. It is usually highest in the evening. Other factors that may affect body temperature are: - A woman's menstrual cycle. In the second part of this cycle, her temperature may go up by 1 degree Fahrenheit or more. - Physical activity, strong emotion, eating, heavy clothing, medicines, high room temperature, and high humidity can all increase body temperature. Fever is an important part of the body's defense against infection. Most bacteria and viruses that cause infections in people thrive best at 98.6°F (37°C). Many infants and children develop high fevers with mild viral illnesses. Although a fever signals that a battle might be going on in the body, the fever is fighting for, not against the person. Brain damage from a fever generally will not occur unless the fever is over 107.6°F (42°C). Untreated fevers caused by infection will seldom go over 105°F (40.6°C) unless the child is overdressed or in a hot place. [Febrile seizures](https://ufhealth.org/adam/1/000980) do occur in some children. Most febrile seizures are over quickly and do not mean your child has epilepsy. These seizures also do not cause any permanent harm. Unexplained fevers that continue for days or weeks are called fevers of undetermined origin (FUO). ## Causes Almost any infection can cause a fever, including: - Bone infections ([osteomyelitis](https://ufhealth.org/adam/1/000437)), [appendicitis](https://ufhealth.org/adam/1/000256), skin infections or [cellulitis](https://ufhealth.org/adam/1/000855), and [meningitis](https://ufhealth.org/adam/1/000680) - Respiratory infections such as [colds](https://ufhealth.org/adam/1/000678) or [flu](https://ufhealth.org/adam/1/000080)\-like illnesses, [sore throats](https://ufhealth.org/adam/1/000655), [ear infections](https://ufhealth.org/adam/1/001336), [sinus infections](https://ufhealth.org/adam/1/000647), [mononucleosis](https://ufhealth.org/adam/1/000591), [bronchitis](https://ufhealth.org/adam/1/001087), [pneumonia](https://ufhealth.org/adam/1/000145), and [tuberculosis](https://ufhealth.org/adam/1/000077) - [Urinary tract infections](https://ufhealth.org/adam/1/000521) - [Viral gastroenteritis](https://ufhealth.org/adam/1/000252) and [bacterial gastroenteritis](https://ufhealth.org/adam/1/000254) Children and adults may have a low-grade fever for 1 or 2 days after some [immunizations](https://ufhealth.org/adam/1/002024). [Teething](https://ufhealth.org/adam/1/002045) may cause a slight increase in a child's temperature, but not higher than 100°F (37.8°C). Autoimmune or inflammatory disorders may also cause fevers. Some examples are: - [Arthritis](https://ufhealth.org/adam/1/001243) or connective tissue illnesses such as [rheumatoid arthritis](https://ufhealth.org/adam/1/000431) and [systemic lupus erythematosus](https://ufhealth.org/adam/1/000435) - [Ulcerative colitis](https://ufhealth.org/adam/1/000250) and [Crohn disease](https://ufhealth.org/adam/1/000249) - [Vasculitis](https://ufhealth.org/adam/1/000874) or [periarteritis nodosa](https://ufhealth.org/adam/1/001438) The first symptom of a cancer may be a fever. This is particularly true of [Hodgkin disease](https://ufhealth.org/adam/1/000580), [non-Hodgkin lymphoma](https://ufhealth.org/adam/1/000581), and [leukemia](https://ufhealth.org/adam/1/001299). Other possible causes of fever include: - [Blood clots](https://ufhealth.org/adam/1/001124) or [thrombophlebitis](https://ufhealth.org/adam/1/001108) - Medicines, such as some antibiotics, antihistamines, and seizure medicines ## Home Care A simple cold or other viral infection can sometimes cause a high fever (102°F to 104°F or 38.9°C to 40°C). This does not mean you or your child has a serious problem. Some serious infections don't cause a fever or can cause a very low body temperature, most often in infants. If the fever is mild and you have no other problems, you do not need treatment. Drink fluids and rest. The illness is probably not serious if your child: - Is still interested in playing - Is eating and drinking well - Is alert and smiling at you - Has a normal skin color - Looks well when their temperature comes down Take steps to lower a fever if you or your child is uncomfortable, vomiting, dried out (dehydrated), or not sleeping well. Remember, the goal is to lower, not eliminate, the fever. When trying to lower a fever: - Do not bundle up someone who has chills. - Remove excess clothing or blankets. The room should be comfortable, not too hot or cool. Try one layer of lightweight clothing, and one lightweight blanket for sleep. If the room is hot or stuffy, a fan may help. - A lukewarm bath or sponge bath may help cool someone with a fever. This is effective after medicine is given -- otherwise the temperature might bounce right back up. - Do not use cold baths, ice, or alcohol rubs. These cool the skin, but often make the situation worse by causing shivering, which raises the core body temperature. Here are some guidelines for taking medicine to lower a fever: - Acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) help reduce fever in children and adults. Sometimes health care providers advise you to use both types of medicine. - Take acetaminophen every 4 to 6 hours. It works by turning down the brain's thermostat. - Take ibuprofen every 6 to 8 hours. Do not use ibuprofen in children 6 months or younger. - Aspirin is very effective for treating fever in adults. Do not give aspirin to a child unless your child's provider tells you to. - Know how much you or your child weighs. Then check the instructions on the package to find the correct dose. - In children 3 months or younger, call your child's provider first before giving medicines. Eating and drinking: - Everyone, particularly children, should drink plenty of fluids. Water, ice pops, soup, and gelatin are all good choices. - In younger children do not give too much fruit juice or apple juice, and do not give sports drinks. - Although eating is fine, do not force foods. ## When to Contact a Medical Professional Contact a provider right away if your child: - Is 3 months or younger and has a rectal temperature of 100.4°F (38°C) or higher - Is 3 to 12 months old and has a fever of 102.2°F (39°C) or higher - Is 2 years or younger and has a fever that lasts longer than 24 to 48 hours - Is older and has a fever for longer than 48 to 72 hours - Has a fever of 105°F (40.5°C) or higher, unless it comes down readily with treatment and the person is comfortable - Has other symptoms that suggest an illness may need to be treated, such as a sore throat, [earache](https://ufhealth.org/adam/1/003046), or [cough](https://ufhealth.org/adam/1/003072) - Has had fevers come and go for up to a week or more, even if these fevers are not very high - Has a serious medical illness, such as a heart problem, sickle cell anemia, diabetes, or cystic fibrosis - Recently had an immunization - Has a new rash or bruises - Has pain with urination - Has a weakened immune system (because of long-term \[chronic\] steroid therapy, a bone marrow or organ transplant, spleen removal, HIV/AIDS, or cancer treatment) - Has recently traveled to another country Contact your provider right away if you are an adult and you: - Have a fever of 105°F (40.5°C) or higher, unless it comes down readily with treatment and you are comfortable - Have a fever that stays at or keeps rising above 103°F (39.4°C) - Have a fever for longer than 48 to 72 hours - Have had fevers come and go for up to a week or more, even if they are not very high - Have a serious medical illness, such as a [heart problem](https://ufhealth.org/adam/60/000775), [sickle cell anemia](https://ufhealth.org/adam/1/000527), [diabetes](https://ufhealth.org/adam/1/001214), [cystic fibrosis](https://ufhealth.org/adam/1/000107), [COPD](https://ufhealth.org/adam/1/000091), or other long-term (chronic) lung problems - Have a new rash or bruises - Have pain with urination - Have a weakened immune system (from chronic steroid therapy, a bone marrow or organ transplant, spleen removal, [HIV/AIDS](https://ufhealth.org/adam/1/000594), or cancer treatment) - Have recently traveled to another country Call 911 or the local emergency number if you or your child has a fever and: - Is crying and cannot be calmed (children) - Cannot be awakened easily or at all - Seems confused - Cannot walk - Has difficulty breathing, even after the nose is cleared - Has blue lips, tongue, or nails - Has a very bad headache - Has a stiff neck - Refuses to move an arm or leg (children) - Has a seizure ## What to Expect at Your Office Visit Your provider will perform a physical exam. This may include a detailed examination of the skin, eyes, ears, nose, throat, neck, chest, and abdomen to look for the cause of the fever. Treatment depends on the duration and cause of the fever, as well as other symptoms. The following tests may be performed: - Blood tests, such as a [CBC](https://ufhealth.org/adam/1/003642) or [white blood cell differential](https://ufhealth.org/adam/1/003657) - [Urinalysis](https://ufhealth.org/adam/1/003579) - [X-ray of the chest](https://ufhealth.org/adam/1/003804) ## Gallery [ Fever is an important part of the body's defense against infection. Most bacteria and viruses that cause infections in humans thrive best at 98.6 degrees F (37 degrees C). Raising the body temperature a few degrees can help the body fight the infection. In addition, a fever activates the body's immune system to make more white blood cells, antibodies, and other infection-fighting agents.](https://ufhealth.org/assets/adam/19700.jpg) [ A thermometer is a useful aid used to measure body temperature. A thermometer is usually filled with mercury. Mercury in the tube rises when expanded by an increase in body temperature.](https://ufhealth.org/assets/adam/9961.jpg) ## References Leggett JE. Approach to fever or suspected infection in the normal host. In: Goldman L, Schafer AI, eds. *Goldman-Cecil Medicine*. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 264. Nield LS, Kamat D. Fever. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. *Nelson Textbook of Pediatrics*. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 201. Last reviewed July 31, 2024 by Charles I. Schwartz, MD, FAAP, Clinical Assistant Professor of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, General Pediatrician at PennCare for Kids, Phoenixville, PA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.. ## Related specialties ## Aftercare and more ## Our locations ## News and patient stories: Fever [More Fever stories](https://ufhealth.org/conditions-and-treatments/fever/stories) ## Latest podcast episodes ## [Have a mild fever? Hold off on medication](https://podcasts.ufhealth.org/have-a-mild-fever-hold-off-on-medication/) For some people, reaching into the medicine cabinet to treat a mild fever is a reflexive action. It might be a good idea to hold off on that. New research suggests that it could be better to let a... ## [Fever during pregnancy increases risk of autism](https://podcasts.ufhealth.org/fever-during-pregnancy-increases-risk-of-autism/) According to the U.S. Centers for Disease Control and Prevention, about one in 80 children in America are now diagnosed with some form of autism every year. As the incidence of this developmental... ## [Fevers could be beneficial](https://podcasts.ufhealth.org/fevers-could-be-beneficial/) Feeling a little hot? It could be a fever coming on. But before you run for the Tylenol, hear this: New research has found that a mild fever could actually be good for you. According to research... [Listen to more Health in a Heartbeat episodes](https://podcasts.ufhealth.org/category/health-in-a-heartbeat/)