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Be careful not to lose muscle](https://www.health.harvard.edu/staying-healthy/trying-to-lose-weight-be-careful-not-to-lose-muscle) [ Is your skin problem actually an autoimmune condition?](https://www.health.harvard.edu/diseases-and-conditions/is-your-skin-problem-actually-an-autoimmune-condition) [ People with diabetes face higher risk of hearing loss](https://www.health.harvard.edu/diseases-and-conditions/people-with-diabetes-face-higher-risk-of-hearing-loss) [ Antibiotic-free fixes for recurrent UTIs](https://www.health.harvard.edu/womens-health/antibiotic-free-fixes-for-recurrent-utis) [ Musculoskeletal syndrome of menopause: When menopause makes you ache all over](https://www.health.harvard.edu/womens-health/musculoskeletal-syndrome-of-menopause-when-menopause-makes-you-ache-all-over) [ When can older women stop getting mammograms?](https://www.health.harvard.edu/womens-health/when-can-older-women-stop-getting-mammograms) [ To lose weight, especially harmful belly fat, combine diet and exercise](https://www.health.harvard.edu/staying-healthy/to-lose-weight-especially-harmful-belly-fat-combine-diet-and-exercise) [ Can men hold off on treating recurring prostate cancer?](https://www.health.harvard.edu/blog/can-men-hold-off-on-treating-recurring-prostate-cancer-202512193108) [ The 7 types of rest and why we need them all](https://www.health.harvard.edu/mind-and-mood/the-7-types-of-rest-and-why-we-need-them-all) [ What are the early warning signs of cervical cancer?](https://www.health.harvard.edu/cancer/what-are-the-early-warning-signs-of-cervical-cancer) 1 / 10 # Fever in Adults Share [Share this page to Facebook](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.health.harvard.edu%2Fdecision_guide%2Ffever-in-adults&display=popup) [Share this page to X](https://twitter.com/intent/tweet?original_referer=https%3A%2F%2Fwww.health.harvard.edu%2Fdecision_guide%2Ffever-in-adults&text=Fever%20in%20Adults%20-%20Harvard%20Health&tw_p=tweetbutton&url=https%3A%2F%2Fwww.health.harvard.edu%2Fdecision_guide%2Ffever-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 - https://www.health.harvard.edu/decision_guide/fever-in-adults>) Copy this page to clipboard Print This Page Click to Print Welcome to this symptom guide about fever. Sorry to hear you have a fever\! This guide is intended for adults who have an abnormally elevated temperature. Although we think of normal body temperature as 98.6 degrees F, body temperature varies -- and so does the definition of fever. Since body temperature rarely climbs above 99.9 degrees without a reason, this guide will consider a fever to be present when the body temperature is 100.0 F (38 degrees C) or higher. While temperatures between 98.6 and 99.9 degrees might be high for you, minor elevations in temperature are less likely to be a true indication of illness and are often within the range of normal variation. To continue reading this article, you must **[log in](https://www.health.harvard.edu/login?redirect_to=https%3A%2F%2Fwww.health.harvard.edu%2Fdecision_guide%2Ffever-in-adults)**. Subscribe to Harvard Health Online Plus (HHO+) to unlock expert-backed health insights, personalized tools, and exclusive resources to feel your best every day. 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Be careful not to lose muscle](https://www.health.harvard.edu/staying-healthy/trying-to-lose-weight-be-careful-not-to-lose-muscle) [ Is your skin problem actually an autoimmune condition?](https://www.health.harvard.edu/diseases-and-conditions/is-your-skin-problem-actually-an-autoimmune-condition) [ People with diabetes face higher risk of hearing loss](https://www.health.harvard.edu/diseases-and-conditions/people-with-diabetes-face-higher-risk-of-hearing-loss) [ Antibiotic-free fixes for recurrent UTIs](https://www.health.harvard.edu/womens-health/antibiotic-free-fixes-for-recurrent-utis) [ Musculoskeletal syndrome of menopause: When menopause makes you ache all over](https://www.health.harvard.edu/womens-health/musculoskeletal-syndrome-of-menopause-when-menopause-makes-you-ache-all-over) [ When can older women stop getting mammograms?](https://www.health.harvard.edu/womens-health/when-can-older-women-stop-getting-mammograms) [ To lose weight, especially harmful belly fat, combine diet and exercise](https://www.health.harvard.edu/staying-healthy/to-lose-weight-especially-harmful-belly-fat-combine-diet-and-exercise) [ Can men hold off on treating recurring prostate cancer?](https://www.health.harvard.edu/blog/can-men-hold-off-on-treating-recurring-prostate-cancer-202512193108) [ The 7 types of rest and why we need them all](https://www.health.harvard.edu/mind-and-mood/the-7-types-of-rest-and-why-we-need-them-all) [ What are the early warning signs of cervical cancer?](https://www.health.harvard.edu/cancer/what-are-the-early-warning-signs-of-cervical-cancer) 1 / 10 ## Free Healthbeat Signup Get the latest in health news delivered to your inbox\! 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Welcome to this symptom guide about fever. Sorry to hear you have a fever\! This guide is intended for adults who have an abnormally elevated temperature. Although we think of normal body temperature as 98.6 degrees F, body temperature varies -- and so does the definition of fever. Since body temperature rarely climbs above 99.9 degrees without a reason, this guide will consider a fever to be present when the body temperature is 100.0 F (38 degrees C) or higher. While temperatures between 98.6 and 99.9 degrees might be high for you, minor elevations in temperature are less likely to be a true indication of illness and are often within the range of normal variation.