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 [Skip to main content](https://www.health.harvard.edu/diseases-and-conditions/treating-fever-in-adults#main-content) [Harvard Health Publishing ](https://www.health.harvard.edu/) [Harvard Health Publishing](https://www.health.harvard.edu/) [HarvardHealthOnline+](https://www.health.harvard.edu/hho-plus?utm_source=site&utm_medium=web&utm_campaign=top_button) Search [Customer Service](https://www.health.harvard.edu/customer-service) [Content Licensing](https://www.health.harvard.edu/licensing) [About Us](https://www.health.harvard.edu/about-us) [Log In](https://www.health.harvard.edu/login) Open mobile menu [Free HealthBeat Signup](https://www.health.harvard.edu/healthbeat) Shop [Subscriptions](https://www.health.harvard.edu/subscribe) [Special Health Reports](https://www.health.harvard.edu/special-health-reports) [Online Courses](https://www.harvardhealthonlinelearning.com/catalog) [Pay Subscription Bill](https://www.health.harvard.edu/pay-bill) [Common Conditions](https://www.health.harvard.edu/category/common-conditions) [Staying Healthy](https://www.health.harvard.edu/category/staying-healthy) [Resources](https://www.health.harvard.edu/resources) [Blog](https://www.health.harvard.edu/blog) [COVID-19 Updates](https://www.health.harvard.edu/diseases-and-conditions/coronavirus-resource-center) Close menu [HarvardHealthOnline+](https://www.health.harvard.edu/hho-plus?utm_source=site&utm_medium=web&utm_campaign=mobile_button) ## Main Content - [Common Conditions](https://www.health.harvard.edu/category/common-conditions) - [Staying Healthy](https://www.health.harvard.edu/category/staying-healthy) - [Resources](https://www.health.harvard.edu/resources) - [Blog](https://www.health.harvard.edu/blog) ## Helpful Links - [Customer Service](https://www.health.harvard.edu/customer-service) - [About Us](https://www.health.harvard.edu/about-us) - [Content Licensing](https://www.health.harvard.edu/licensing) - [Free Healthbeat Signup](https://www.health.harvard.edu/healthbeat) - [Subscriptions](https://www.health.harvard.edu/subscribe) - [Special Health Reports](https://www.health.harvard.edu/special-health-reports) - [Online Courses](https://www.harvardhealthonlinelearning.com/) - [Pay Subscription Bill](https://www.health.harvard.edu/pay-bill) Close Recent Articles [ Understanding food noise - and how to turn down the volume](https://www.health.harvard.edu/diet-and-nutrition/understanding-food-noise-and-how-to-turn-down-the-volume) [ Remedies for motion sickness: What works?](https://www.health.harvard.edu/preventive-care/remedies-for-motion-sickness-what-works) [ 4 keys to a heart-healthy diet](https://www.health.harvard.edu/heart-health/4-keys-to-a-heart-healthy-diet) [ Understanding exercise heart rate zones](https://www.health.harvard.edu/exercise-and-fitness/understanding-exercise-heart-rate-zones) [ Resistant starch: Can you make the carbs you eat a little healthier?](https://www.health.harvard.edu/diet-and-nutrition/resistant-starch-can-you-make-the-carbs-you-eat-a-little-healthier) [ Harvard study: A couple of daily cups of coffee or tea linked to lower dementia risk](https://www.health.harvard.edu/diet-and-nutrition/harvard-study-a-couple-of-daily-cups-of-coffee-or-tea-linked-to-lower-dementia-risk) [ Does everyone benefit from cutting saturated fat in their diet?](https://www.health.harvard.edu/heart-health/does-everyone-benefit-from-cutting-saturated-fat-in-their-diet) [ How to treat shoulder impingement](https://www.health.harvard.edu/bones-and-joints/how-to-treat-shoulder-impingement) [ Beyond protein: 6 other nutrients that help prevent muscle loss](https://www.health.harvard.edu/diet-and-nutrition/beyond-protein-6-other-nutrients-that-help-prevent-muscle-loss) [ Advancements in knee replacement: More precise and personalized](https://www.health.harvard.edu/bones-and-joints/advancements-in-knee-replacement-more-precise-and-personalized) 1 / 10 # Fever in adults: When to worry ## Infection is a common cause of fever, but other conditions can also bring the heat.  [Fever](https://www.health.harvard.edu/a_to_z/fever-a-to-z) is one of the body's most effective ways of fighting infection. It is part of your body's defense against infection-causing germs. You get a fever most often when your body is trying to kill infectious invaders such as viruses or bacteria. A higher body temperature helps the immune system respond more vigorously to the attack, and makes it harder for these microbes to survive. ## What is considered a fever in adults? The average body temperature is 98.6° F (37°C). But "normal" body temperature varies from person to person. It also changes during the day, rising a bit after you eat or exercise. Body temperature is often higher in the afternoon than it is when you wake up in the morning. [](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=523536412&PID=0&textadID=0&tc=1&rnd=7351205261&scheduleID=3142476&adSize=0x0&matches=%5B%22inurl%3Adiseases-and-conditions%22%2C%22inurl%3Afever-in-adults%22%5D&mt=1775079223286288&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&request_uuid=f5a54c2d-231f-49b3-8776-856a95d3d2cc&hc=3a67033d3484750716b1612044b8dba089b20c10&location=) Fever means a body temperature of 100.4° F (38°C) or higher. ## High fever in adults While any temperature above your normal temperature range is considered a fever, there are different levels of fever [severity](https://www.ncbi.nlm.nih.gov/books/NBK562334/): - **Low-grade:** 99.1 to 100.4 F (37.3 to 38.0 C) - **Moderate-grade:** 100.6 to 102.2 F (38.1 to 39.0 C) - **High-grade:** 102.4 to 105.8 F (39.1 to 41 C). ## When to worry about fever If you have a fever over 104°F (40°C), you should call your doctor. Seek medical help right away if you have a fever along with any of these symptoms: [](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=523669234&PID=0&textadID=0&tc=1&rnd=7351205261&scheduleID=3245955&adSize=0x0&matches=%5B%22inurl%3Adiseases-and-conditions%22%2C%22inurl%3Afever-in-adults%22%5D&mt=1775079223286415&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&request_uuid=f5a54c2d-231f-49b3-8776-856a95d3d2cc&hc=78eb58e75092a2852b1118611dce9bd98f0be03d&location=) - seizure - loss of consciousness - confusion - stiff neck - trouble breathing - severe pain anywhere in the body - swelling or inflammation of any part of the body - vaginal discharge that is discolored or smells bad - pain when urinating or urine that smells bad. ## Causes of fever An infection, such as the [flu](https://www.health.harvard.edu/topics/cold-and-flu), is the most common cause of fever. Other conditions can also cause a fever. These include diseases that produce [inflammation](https://www.health.harvard.edu/staying-healthy/playing-with-the-fire-of-inflammation), such as [rheumatoid arthritis](https://www.health.harvard.edu/pain/exercise-can-ease-rheumatoid-arthritis-pain); reactions to drugs or vaccines; and even certain types of cancers. ## Accompanying symptoms The following symptoms may also accompany fever: - sweats - chills - headache - achy muscles - lack of desire to eat - rash - restlessness - weakness. You may be interested in...  ## Food is Medicine As nutrition research has accumulated, so has a growing consensus that diet ought to play a larger role in society’s overall approach to health. This “food is medicine” philosophy dovetails with a rising interest in lifestyle medicine and whole-person health care. The goal is not simply to treat disease, but to target the root causes of chronic conditions and, ideally, prevent them before they arise. [LEARN MORE](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=524382211&PID=0&textadID=0&tc=1&rnd=7351205261&scheduleID=3703307&adSize=0x0&matches=%5B%22diseases%22%5D&mt=1775079223286497&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&request_uuid=f5a54c2d-231f-49b3-8776-856a95d3d2cc&hc=d9009b452a91dce6dc61ae5b58338e09dc2059d5&location=) A very high fever can cause confusion, extreme sleepiness, irritability, and seizures. ## Diagnosing the cause of a fever To help determine why you have a fever, your doctor will ask you about: - other symptoms such as coughing, abdominal pain, vomiting, diarrhea, or pain when urinating - recent surgeries or injuries - recent vaccinations - new drugs you may be taking - recent travel, particularly travel abroad. ## How to treat a fever at home By itself, fever is usually harmless, though a high fever can be miserable. These steps may help you feel better: - Drink plenty of fluids to help cool your body and prevent dehydration. - Eat light foods that are easy to digest. - Get plenty of rest. - Take ibuprofen (Advil, Motrin, or others), naproxen (Aleve, Naprosyn, or others), or acetaminophen (Tylenol, others) to help relieve head and body aches and lower your temperature. - Take a slightly warm (not cool) bath, or apply damp washcloths to the forehead and wrists. You may be interested in...  ## Discovering Functional Fitness As we get older, everyday tasks—squatting to weed your garden, reaching for a book on a high shelf—can become harder to do without pain or discomfort. It doesn’t have to be this way! Workouts that focus on “functional fitness” can help you prevent and even reverse these changes and so you can enjoy greater strength, power, flexibility, and mobility in everyday movements. What the heck is functional fitness? Functional fitness improves your ability to carry out daily activities more easily and more confidently. This is the kind of exercise you need to stay active and independent, on your own terms, doing what you love to do. And the benefits go beyond muscle strength and mobility. [LEARN MORE](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=524382528&PID=0&textadID=0&tc=1&rnd=7351205261&scheduleID=3703606&adSize=0x0&matches=%5B%22diseases%22%5D&mt=1775079223286588&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&request_uuid=f5a54c2d-231f-49b3-8776-856a95d3d2cc&hc=5f77a6d449f2c523d542e3b8e7d5b59e0574439e&location=) **Image: yacobchuck/Getty Images** Share [Share this page to Facebook](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&display=popup) [Share this page to X](https://twitter.com/intent/tweet?original_referer=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&text=Fever%20in%20adults:%20when%20to%20worry%20-%20Harvard%20Health&tw_p=tweetbutton&url=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults) [Share this page via Email](<mailto:?subject=Great health news for you from the experts at Harvard&body=Check out this link from Harvard Health: Fever in adults: when to worry - https://www.health.harvard.edu/diseases-and-conditions/treating-fever-in-adults>) Copy this page to clipboard Print This Page Click to Print ## Disclaimer: As a service to our readers, Harvard Health Publishing provides access to our library of archived content. 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Recent Articles [ Understanding food noise - and how to turn down the volume](https://www.health.harvard.edu/diet-and-nutrition/understanding-food-noise-and-how-to-turn-down-the-volume) [ Remedies for motion sickness: What works?](https://www.health.harvard.edu/preventive-care/remedies-for-motion-sickness-what-works) [ 4 keys to a heart-healthy diet](https://www.health.harvard.edu/heart-health/4-keys-to-a-heart-healthy-diet) [ Understanding exercise heart rate zones](https://www.health.harvard.edu/exercise-and-fitness/understanding-exercise-heart-rate-zones) [ Resistant starch: Can you make the carbs you eat a little healthier?](https://www.health.harvard.edu/diet-and-nutrition/resistant-starch-can-you-make-the-carbs-you-eat-a-little-healthier) [ Harvard study: A couple of daily cups of coffee or tea linked to lower dementia risk](https://www.health.harvard.edu/diet-and-nutrition/harvard-study-a-couple-of-daily-cups-of-coffee-or-tea-linked-to-lower-dementia-risk) [ Does everyone benefit from cutting saturated fat in their diet?](https://www.health.harvard.edu/heart-health/does-everyone-benefit-from-cutting-saturated-fat-in-their-diet) [ How to treat shoulder impingement](https://www.health.harvard.edu/bones-and-joints/how-to-treat-shoulder-impingement) [ Beyond protein: 6 other nutrients that help prevent muscle loss](https://www.health.harvard.edu/diet-and-nutrition/beyond-protein-6-other-nutrients-that-help-prevent-muscle-loss) [ Advancements in knee replacement: More precise and personalized](https://www.health.harvard.edu/bones-and-joints/advancements-in-knee-replacement-more-precise-and-personalized) 1 / 10 ## Related Topics [ Healthy aging and longevity The complicated risks of simple cold remedies](https://www.health.harvard.edu/healthy-aging-and-longevity/the-complicated-risks-of-simple-cold-remedies) [ Healthy aging and longevity When will we see a "one-and-done" flu shot?](https://www.health.harvard.edu/healthy-aging-and-longevity/when-will-we-see-a-one-and-done-flu-shot) [ Healthy aging and longevity Why do we need new flu shots every year?](https://www.health.harvard.edu/healthy-aging-and-longevity/why-do-we-need-new-flu-shots-every-year) [Colds and flu](https://www.health.harvard.edu/topics/colds-and-flu) [Healthy aging and longevity](https://www.health.harvard.edu/topics/healthy-aging-and-longevity) [Immune and infectious diseases](https://www.health.harvard.edu/topics/immune-and-infectious-diseases) ## Free Healthbeat Signup Get the latest in health news delivered to your inbox\! 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 [Fever](https://www.health.harvard.edu/a_to_z/fever-a-to-z) is one of the body's most effective ways of fighting infection. It is part of your body's defense against infection-causing germs. You get a fever most often when your body is trying to kill infectious invaders such as viruses or bacteria. A higher body temperature helps the immune system respond more vigorously to the attack, and makes it harder for these microbes to survive. ## What is considered a fever in adults? The average body temperature is 98.6° F (37°C). But "normal" body temperature varies from person to person. It also changes during the day, rising a bit after you eat or exercise. Body temperature is often higher in the afternoon than it is when you wake up in the morning. [](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=523536412&PID=0&textadID=0&tc=1&rnd=7351205261&scheduleID=3142476&adSize=0x0&matches=%5B%22inurl%3Adiseases-and-conditions%22%2C%22inurl%3Afever-in-adults%22%5D&mt=1775079223286288&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&request_uuid=f5a54c2d-231f-49b3-8776-856a95d3d2cc&hc=3a67033d3484750716b1612044b8dba089b20c10&location=) Fever means a body temperature of 100.4° F (38°C) or higher. ## High fever in adults While any temperature above your normal temperature range is considered a fever, there are different levels of fever [severity](https://www.ncbi.nlm.nih.gov/books/NBK562334/): - **Low-grade:** 99.1 to 100.4 F (37.3 to 38.0 C) - **Moderate-grade:** 100.6 to 102.2 F (38.1 to 39.0 C) - **High-grade:** 102.4 to 105.8 F (39.1 to 41 C). ## When to worry about fever If you have a fever over 104°F (40°C), you should call your doctor. Seek medical help right away if you have a fever along with any of these symptoms: [](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=523669234&PID=0&textadID=0&tc=1&rnd=7351205261&scheduleID=3245955&adSize=0x0&matches=%5B%22inurl%3Adiseases-and-conditions%22%2C%22inurl%3Afever-in-adults%22%5D&mt=1775079223286415&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&request_uuid=f5a54c2d-231f-49b3-8776-856a95d3d2cc&hc=78eb58e75092a2852b1118611dce9bd98f0be03d&location=) - seizure - loss of consciousness - confusion - stiff neck - trouble breathing - severe pain anywhere in the body - swelling or inflammation of any part of the body - vaginal discharge that is discolored or smells bad - pain when urinating or urine that smells bad. ## Causes of fever An infection, such as the [flu](https://www.health.harvard.edu/topics/cold-and-flu), is the most common cause of fever. Other conditions can also cause a fever. These include diseases that produce [inflammation](https://www.health.harvard.edu/staying-healthy/playing-with-the-fire-of-inflammation), such as [rheumatoid arthritis](https://www.health.harvard.edu/pain/exercise-can-ease-rheumatoid-arthritis-pain); reactions to drugs or vaccines; and even certain types of cancers. ## Accompanying symptoms The following symptoms may also accompany fever: - sweats - chills - headache - achy muscles - lack of desire to eat - rash - restlessness - weakness. You may be interested in...  As nutrition research has accumulated, so has a growing consensus that diet ought to play a larger role in society’s overall approach to health. This “food is medicine” philosophy dovetails with a rising interest in lifestyle medicine and whole-person health care. The goal is not simply to treat disease, but to target the root causes of chronic conditions and, ideally, prevent them before they arise. [LEARN MORE](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=524382211&PID=0&textadID=0&tc=1&rnd=7351205261&scheduleID=3703307&adSize=0x0&matches=%5B%22diseases%22%5D&mt=1775079223286497&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&request_uuid=f5a54c2d-231f-49b3-8776-856a95d3d2cc&hc=d9009b452a91dce6dc61ae5b58338e09dc2059d5&location=) A very high fever can cause confusion, extreme sleepiness, irritability, and seizures. ## Diagnosing the cause of a fever To help determine why you have a fever, your doctor will ask you about: - other symptoms such as coughing, abdominal pain, vomiting, diarrhea, or pain when urinating - recent surgeries or injuries - recent vaccinations - new drugs you may be taking - recent travel, particularly travel abroad. ## How to treat a fever at home By itself, fever is usually harmless, though a high fever can be miserable. These steps may help you feel better: - Drink plenty of fluids to help cool your body and prevent dehydration. - Eat light foods that are easy to digest. - Get plenty of rest. - Take ibuprofen (Advil, Motrin, or others), naproxen (Aleve, Naprosyn, or others), or acetaminophen (Tylenol, others) to help relieve head and body aches and lower your temperature. - Take a slightly warm (not cool) bath, or apply damp washcloths to the forehead and wrists. You may be interested in...  As we get older, everyday tasks—squatting to weed your garden, reaching for a book on a high shelf—can become harder to do without pain or discomfort. It doesn’t have to be this way! Workouts that focus on “functional fitness” can help you prevent and even reverse these changes and so you can enjoy greater strength, power, flexibility, and mobility in everyday movements. What the heck is functional fitness? Functional fitness improves your ability to carry out daily activities more easily and more confidently. This is the kind of exercise you need to stay active and independent, on your own terms, doing what you love to do. And the benefits go beyond muscle strength and mobility. [LEARN MORE](https://servedbyadbutler.com/redirect.spark?MID=186626&plid=2650436&setID=812675&channelID=0&CID=862911&banID=524382528&PID=0&textadID=0&tc=1&rnd=7351205261&scheduleID=3703606&adSize=0x0&matches=%5B%22diseases%22%5D&mt=1775079223286588&spr=1&referrer=https%3A%2F%2Fwww.health.harvard.edu%2Fdiseases-and-conditions%2Ftreating-fever-in-adults&request_uuid=f5a54c2d-231f-49b3-8776-856a95d3d2cc&hc=5f77a6d449f2c523d542e3b8e7d5b59e0574439e&location=) **Image: yacobchuck/Getty Images**