Have a Fever Over 100? Here’s What to Do About Fever in Adults

A fever is defined as a body temperature above 100.4°F (38°C). A normal oral temperature for a resting, healthy adult is about 98.6°F (37°C). However, what is considered “normal” can vary based on age, race, and other factors e.g. in an individual > 70 years old, a normal temp could be lower at 96.8°F (36°C). Furthermore, a person’s temperature can go up or down 1 to 2 degrees throughout the day and vary depending not only on time of day but also based on activity level, one’s environment (hot, cold, etc.), hydration status, or even medications that he/she may be taking.

Fever is a sign of inflammation, meaning that it most commonly indicates that there is an underlying illness (such as an infection: cold, etc.) or even a bodily injury. It may also be associated with certain autoimmune diseases. Less commonly, it may be caused by certain medications that one is taking. A fever, in and of itself, however, is not a disease.

A fever appears to be one way your body fights illness i.e. your body raises its temperature via its internal thermostat (located within a portion of the brain called the hypothalamus). It does this in response to infection or inflammation to help your immune system to defeat the offending agent. Although it may not be comfortable, a temperature of up to 102°F is generally safe in adults. In fact, most healthy adults can even tolerate a fever as high as 103°F to 104°F for short periods of time without having any significant problems. Body temperatures usually return to normal once the illness goes away. Click here for a list of fever symptoms in adults.

What is the difference Between Fever and Hyperthermia?

Fever and hyperthermia are commonly confused for one another. Hyperthermia is just another word for overheating. Basically, the body is working fine (i.e. without infection) and the thermostat has not been raised (as with fever), but for some reason, the body’s ability to get rid of heat is impaired. This most commonly occurs when one is vigorous exercising in hot temperatures. You are also more at risk if you are not well hydrated. 

Ranges in Body Temperatures

While there are numerous definitions of fever or pyrexia, the CDC defines a fever as a temperature above 100.4°F (38°C). However, it is important to keep in mind, that in certain populations, like the elderly, lower temperatures than 100.4 may also be indicative of a fever, as the elderly are not able to raise their body temperatures as easily as the young.

Here are some other definitions related to body temperature: 

  • Normal: temperatures between 97.7°F (36.5°C) and 99°F (37.2°C)
  • Low-grade fever: temperatures between 99°F (37.2°C) and 100.4°F (38°C)
  • Fever (pyrexia): temperatures between 100.4°F (38°C) and 105.8°F (41°C)
  • Hyperpyrexia: temperatures between 105.8°F (41°C) and 109.4°F (43°C)
  • Temperatures above 109.4°F (43°C) are usually fatal

Symptoms of Fever

Fevers can cause a wide variety of different symptoms. The most common symptoms are listed below:

    1. Muscle aches
    2. Headaches
    3. Irritability
    4. Chills
    5. Loss of appetite
    6. Sweating
    7. Generalized weakness

Click here for a list of fever symptoms in adults.

How to Take Your Temperature – Fever in Adults

Adults should use a digital thermometer to take their temperature under the tongue. Tympanic membrane (ear) and forehead (temporal artery) measurements are also fairly accurate. 

Taking a temperature under the armpit is not very accurate but can be a quick way to take one’s temperature. 

How to Take Your Temperature – Fever in Children

When taking a child’s temperature, a digital thermometer should be placed under the tongue. Tympanic membrane (ear) and forehead measurements are also fairly accurate. 

In infants, identifying the most accurate temperature can be very important. As such, rectal temperatures should be taken. This is actually the most accurate way to take a temperature. 

How to Take Your Temperature – Thermometers

Wash your hands with soap and warm water prior to using any thermometer. 

Mercury Thermometer

With how affordable digital thermometers are nowadays, use of your old mercury thermometers should be avoided.

Mercury is poisonous and is risk at being released when a glass thermometer breaks. Furthermore, they are not as accurate as the latest digital thermometers.

What to Do if a Mercury Thermometer Breaks.

Digital Thermometers

Digital thermometers are affordable and readily available nowadays. They are accurate and easy to read as they have a digital display for numbers.

Click here for a list of good thermometers. Before using, make sure the thermometer is clean and turned on. Again, wash your hands with soap and warm water. Follow the manufacturers instructions regarding appropriate and accurate usage. Clean the thermometer before you put it away.

Fever in adults – How to Treat a Fever

  • Stay hydrated. Water is best. Your body may try to cool itself by sweating and you should replace this loss of fluid.
  • Take your temperature regularly. Keep track of what it is. 
  • Take your temperature more frequently if your symptoms change e.g. if you start vomiting
  • For fevers that are uncomfortable (e.g. associated muscle aches, headaches) you can take acetaminophen or ibuprofen. These medications help to reset your body’s thermostat and drive temperatures down.
  • Do not give aspirin or products that contain aspirin to children or teens under the age of 20. This can potentially cause Reye syndrome, a potentially dangerous condition
  • Watch for signs of dehydration. Dehydration can happen if the fever causes you to sweat excessively, have vomiting, or diarrhea. Signs of dehydration include thirst, dry skin, dry mouth, chills, feeling tired or weak, and dark-colored urine.
  • Other fever remedies for adults.

When to Call Your Doctor

  • If your fever is over 103°F 
  • Persistent fever. Many viral illnesses, especially the flu, cause fevers of 102°F or higher for short periods of time (up to 12 to 24 hours).
  • If your fever is associated with: 
    • Shortness of breath, chest pain 
    • Severe cough 
    • Seizures 
    • Confusion 
    • Persistent vomiting or diarrhea 
    • Severe headache 
    • Skin rash
    • Sensitivity to bright light and/or neck stiffness (could indicate meningitis – an infection of the lining of the brain, spinal cord)
    • Severe abdominal pain (could indicate gastroenteritis, appendicitis, or other abdominal infection)
    • Pain with urination (could indicate a urinary tract infection)

Treatment for Hyperthermia 

Again it is important to remember that hyperthermia is not the same thing as a fever. Again, as it is the result of overheating, in most cases it will return to normal after you have rested for an hour or so in a cool room. Make sure to drink plenty of fluids and to avoid exercising too vigorously outside on very hot days. 

Hyperthermia can be more dangerous than a fever. In particular, if your temperature rises above 104°F and is associated with other symptoms, this is called a heatstroke. This is a medical emergency and should be treated as such. Call 911. Symptoms may include:

  • Confusion 
  • Vomiting 
  • Slurred speech
  • Racing heart
  • Rapid breathing 

Fever in Newborns and Children

Fevers in newborn and children are often treated differently than fevers in adults. Please refer to the following links:

Fever in newborns can be serious and should not be ignored

Fever in Young Children (Toddlers) 

Remedies for fever in children


Note that the information in this article is purely informative and should never be used in place of the advice of your treating physicians.


  1. I had a temperature of 104.9 for several months. I lowest it got was 102.9. The highest it got was 105.9 for day’s. I was in the hospital from 4jun01 till 9sep01 at which point I walked out of the hospital. I went from 187 to 130. The Dr ran test after test and 6 big syringes 6x a day. They never figured it out. so, I left. I went to Tennessee for 2 months to get better to only come home and get sick again. I was so delirious that she said I was the million dollar man and my reply was that I won the lottery? Million’s on test and nothing. Come to find out I had black mold in my home. It almost cost me my life and they never figured it out. Tore out 18’x 40′ section of my and wahala, problem solved. It was truly a miracle for me and a tragical screw up for the dr’s and the hospital. I won….. Thank GOD

  2. If my normal body temperature tends to be between 36.1 and 36.6 generally, and I have been lately frequently recording a temperature of between 37.2 and 37.8 or thereabouts, with sensations of hot flushes and profuse sweating, could this be an indication that I have a fever? Thanks in advance for any info, if anybody cares to reply to me.

  3. Flu-like symptoms but only a low grade fever between 99.9 and 101.8? I’m going on day three of this. I don’t know if this is a cold or a flu. I usually don’t get fevers with a cold. I went in for a UTI 4 days ago. Two days after going to the doctor I started feeling ill. I’m on antibiotics for the UTI and those painful symptoms have gone away.

    I’ve had a rough week…

  4. I came to this page because I woke up with chills, my temp 8s 101.2 and I’m a 55 year old Male. Coughing up alot of mucus. THANK God for mucinex. That some good stuff, no pun intended:).. Anyway I feel awful but tylenol should help

  5. For all the people making rude remarks….you criticize others for asking a question, but here you are. On the same forum. Just trolling to make ugly remarks. Tells us all we need to know about what kind of person you are.

  6. if you have a fever of 100.1,how long will it take to go down?

  7. I’ve had a fever everyday between 99 and 102.9 for 8 months straight. Specialist are still trying to figure out the cause. Praise God I have dual insurance!

  8. Avatar Enough is enough says

    I see some of these comments are old but still people are asking questions. I truly hope no one’s life depends on it – especially if it was about a child. Forums and articles should never be for possibly urgent matters. Medical care can be expensive but the alternative can be worse if left untreated.
    Maybe the best answer is add a “z” to your last name, learn Spanish and look blankly at the window in an ER. It’ll more than likely be free. After all we are the land of the free or at least that’s the way it’s being interpreted. Oh and repeat same method if you commit a crime.

  9. My mum went to hospital for a leg operation now she has Lemonia And a temp of 40deg is she safe in hospital she is all I have left and I’ can’t sleep can’t eat just crying is she going to be ok please give me some good advice not bad

  10. What do i do if i have fever but im allergic to tylenol ibruprophen, advil, aleve, naproxen 😔 help
    Im allergic even liquids/kids dosage…. i swell and everything itches

  11. Avatar Laurie Falk says

    Can a person get the chills and a slight fever if they don’t put the heat on in the house when it is 36 degrees outside ?? I had the same thing two weeks ago when it got very cold out side and I didn’t put the heat on in the house to save money

  12. Avatar Canadian Nursing student says

    Hi nursing student here!
    I have finally broken my fever after 3 days! I was dangerously high, at 40 degrees Celsius (104 farenheit). If I got up to 41 Celsius (105.8 farenheit) I would had to go to the Hospital. With a temperate that high (41’C) your brain can swell, you are at high risk of slipping into a coma and can cause brain damage. This article calls it “tissue damage” but it’s important to know that really means COMA AND POSSIBLE DEATH.

    If you currently have a fever it is vitally important to take a fever reducer like Advil or Tylenol consistently as per the instructions on the box. Do not stop taking it until your fever is down. If you are unable to get your fever down after 2 or 3 days you need to see a doctor. I live in Canada so I have the privilege of free healthcare, but please know a fever can be dangerous if not fatal.

    Do NOT go to work or school. Do not work out or do strenuous activities. Rest, drink fluids, watch a show on Netflix, and keep taking your Tylenol!!

  13. Thanks for the informative article. But some of the comments made me really sad. Extremely sad when people lack compassion and instead of saying soothing words for those suffering try to rub them off the wrong way. Live and Let Live. May God Bless all those who are suffering and May God Bless All of Us.

  14. Avatar Prabhat Pradhan says

    My wife has appendicitis surgery and there after she suffer fever from 15 days what is the cause …first she got UTI now it’s normal …and her husband pilory test is positive

  15. Avatar Need Relief Now says

    I have been burning up with temps of 101-104 since 3 days ago. I have been treated for malaria and strep throat but it’s not really working. I just came back from vacation in the USA and I am wondering if its the flu. I have had malaria in the past and it didn’t last this long with treatment and I have never been this sick with malaria. I’ll go to the doc tomorrow to check for flu in case thats the cause.

  16. Avatar Tonya Key says

    Most hospital’s have payment plans and even help you get Medicaid. All three of the hospital’s in Mobile will take anyone.. with or without insurance. And it’s a good thing… I have kidneys stones constantly, sepsis 5 times, surgery 10 times and they still see me. Only half the time have I had insurance.

  17. Avatar Young and successful says

    Hey just saying…I’m in my mid 20s, hav a wife and baby have insurance for all 3 of us have 2 cars and a great apartment. But gloating but I work an entry level job that has benefits and have built this all myself. It is not hard.

  18. Avatar Dying is ok in a cruel world. says

    When you are so sick you feel like you are going to die and check your symptoms for help, you also end up reading cruel people’s comments and want to just freaking die anyways. Thanks. I don’t have have 32000 for my treatment.. At this point, who wants to live in a world where you can only survive if you do something to make big bucks. Like the billionaires who make money flooding our Earth with toxins, trading stocks of businesses that hurt our planet, or the people who steal, scam and hurt others… I don’t hurt others, but yet I am unworthy and going to die bc of money. Ok. If that’s how you people feel, I seriously welcome death. Thanks for the nudge, I hope you are proud of yourself.

  19. If you see a doctor and he gives you medicine for your symptoms, you will be all better in 7-10 days. If you don’t see a doctor and take no meds, you will be better in 7-10 days.

  20. Jennifer D, when you say “First, Shut off your cell phones, cable, and internet and either buy insurance or go to ANY doc/walk-in clinic! ”

    REALLY? I don’t blame the government but I only pay $30 for Boost cellphone and $45 for internet. I don’t have cable. Please tell me where I can get insurance for $75 a month ! I live in Texas where idiots rule the government ( Google Louie Gohmert and see what I mean). I have a job but don’t qualify for Obamacare because I don’t make enough and don’t qualify for Medicaid because the state didn’t expand it like other states did. If I want insurance it costs me around $800 a month and if I buy insurance I won’t have for food.

    I see how compassionate you are, NOT. I’m sure you go to church every Sunday and tell everybody what a great person you are. Well let me be one who says you have a lot to learn and very far to go.

  21. You guys are just mean. Sometimes people are just trying to get some information. I have insurance but nowadays there’s so much information on the Internet that can help us decide if we should go see them or not in many cases. What is this stuff about people with no insurance. It’s a hard world for a lot of people. Get over yourself not everybody was born with a silver spoon up their bottom to say it nicely. Rob

  22. Avatar Jennifer D says

    First, Shut off your cell phones, cable, and internet and either buy insurance or go to ANY doc/walk-in clinic! They take cash!! Amazing concept! Priorities are questionable when people blame the government for lack of care instead of taking responsibility for one’s health. God help us!

  23. I have had a low grade fever for 6 days. I was diagnosed with lung cancer since January. I don’t think this is good news. Am going to the doc tomorrow. Will let you know how it goes.

  24. Avatar Brenda Chipman says

    Oh, I know I may have some spelling grammar issues and left out words,I have ms it makes it hard to sometimes. Have a Blessed Day

  25. Avatar Brenda Chipman says

    For those who have no insurance, Do not go to a private pay hospital, every city has a hospital that helps, you get seen there and they can help you get temp Medicaid to help those with the bill. They don’t tell you about the program. But they are there, it’s how it works they are more concerned about you as a patient.. They can be dealt with later. The program is strictly for those in need and they ask you questions about income and they will check so the program how they can stay funded if you fall between the cracks they will still help you. Why do I know about this I have a friends who handle it. Before you say anything I have good insurance not welfare insurance either. People need to open there hearts not everyone wants to scam the government.

  26. I had a sudden fever the other night but it only lasted an hour and a half. Strangest thing ever. Had cold shivers, freezing and then had fever of 101.7 body ached like the flu eyes hurt then I was fine after an hour and a half. Never have I had this happen before. Was laughing very hard then this came on. Just weird. Anyone hear of something like this before?

  27. It’s called get an education and get a job! I’m not even republican and I feel this way! Sorry u may not have had many chances and probably grew up in a poor family, but really it’s no excuse! And why do u think there is welfare anyway? Get on it if u need help!

  28. If you are lucky enough to live in a country where doctors visits are free (australia, new zealand, canada, UK), theres no need to “use your money wisely” but it is still hard to get out of bed and go to the doctors if you have a fever!

  29. Avatar Pissed off at "use your money wisely" says

    Use your money wisely says:
    February 16, 2016 at 10:08 pm

    For the people who complain about they don’t have money to see a doctor. Its like saying they rather die than paying to see a doctor. Why do you need money if you are dead? Amusing
    REALLY!!!! You are a insensitive ****. From your title “Use your money wisely” it appears you never had a financial burden….
    Karma what goes around comes around douche bag! I have health insurance and been in this situation where the deductible is outrageous and had to save for procedures.

  30. I’d just like to say how empathetic I am to all of you. Really. I don’t have health insurance either, nor can I afford it. And I’ve had MRSA staph infection for over a month accompanied by a fever of 101° +. All I want to say is wtf American health care. God bless ya’ll

  31. Avatar Roli Asthana says

    my daughter has 101 fever from last 3 days.she was taking paracetemol 6 hourly.now she has 102.6 degree.pain at the back of neck and heavyness in head,what it can be

  32. Avatar Use your money wisely says

    For the people who complain about they don’t have money to see a doctor. Its like saying they rather die than paying to see a doctor. Why do you need money if you are dead? Amusing

  33. Dave,
    I had the same thing…persistent fever for weeks. The doctor finally discovered I had a virus…CMV which is similar to Mono. Ask your doctor about it.

  34. My wife has had a semi-low grade fever of 101-102 F for over thirty days in a row. She has had blood work done twice, showing No Infection anywhere. She also has had a headache daily too since the onset of the fever. what could be causing this?? Her Doc/Primary phy. has no answers??
    Please, someone help me find an answer! My wife is miserable everyday for over a Month Straight!!

  35. Avatar saran walker says

    I have pain all in my face I have a very bad headache if I bend over I feel like I am going to pass out I am very light headed my whole body hurts I have a low grade fever of 100.0 I been sneezing all day and coughing my throat hurts a lil and I have diarrhea and I have no appetite can you tell me what this is and What I can do

  36. arsalan,
    I am in fever since 2 days….doctor give me some medicine …..and also give me antibiotic(calamox) for my flu,cold,feverand headache due to flu..i am 18 year old.PLEASE GIVE ME ADVICE. I STILL IN COLD WHICH ALSO EFFECT ON MY FAMILY ALSO…..

  37. Cindy, this is just the information I was looking for about when it is time to call the doctor. As an adult, I feel like I don’t go to the doctor as much as I was when I was a kid. Maybe it is because I am now in charge of taking myself to the doctor and I am not always sure when I need to go. Lately I have been feeling kind of off. I am in pain but I am not sure what caused it. Maybe it is a fever? Maybe I should take the advice in this article and go ahead and call the doctor.

  38. Hi, I have had a fever ranging from 102.4-103.3 for the last 4 full day. I feel absolutely miserable. I also have this awful cough that started 2 days ago and is causing my throat to be so sore. My head hurts I have chills and hot flashes when i take the tylenol and motrin. even my goose bumps hurt. my whole body is killing me. I dont know what to do. my lungs are clear so its not pnemonia. but i do not know what else it could be.

  39. Sir

    Please tell my son is have fever 101 degree just half an hour please give advise

  40. My bf is having a fever of 103. Is it dangerous ? Please tell…

  41. Good

  42. hi my wife is at hospital for 10 days now and they did so many test. they cant find the fault .plz can u help me,thx

  43. Media Partners says:
    April 23, 2013 at 10:57 am

    Just because you don’t have insurance, doesn’t mean you can’t see a doctor. They will take cash.

    They take cash? Well isn’t that convenient for all those people who have a couple grand just burning a hole in their pockets. Do you have any idea how much a visit to the ER costs? Good article but stupid comment.

  44. I had a fever with the intensity of 104° F last night. That was the first time for me and hope it would never happen again. Thank you God for saving me.

  45. I started with a temp yesterday night of 103.8 and i got it to go down to 98.6….I woke up it was 101.5…I took tylenol and it broke the fever and i was fine until the tylenol wore off and my temp went to 99.7 then on to 101.1….I keep taking tylenol every 6 hours it helps but i dont have a cough all the time bits rarely and no sore throat…Dry mouth here and there and i have soreness in my neck and pains in my head when i do cough…..Help any advice

  46. And even when you have insurance, there are deductibles and co-payments, and lots of things end up getting paid out of your pocket anyway. That’s even more true for most people since Obamacare went into effect.

    If someone has a temperature of 106, and if it’s accurate and sustained, they should go to the ER. The ER is not going to let you die, even if you have no insurance or money.

  47. My mom has a fever on Christmas! I’m going to cry.I hope she won’t die.
    I fell upset.

  48. Avatar James Ziessler says

    My wife has had a fever 1.2 or 103 102 the last four days no apo tote can’t keep liquids down dizzy sleeps alot and headach

  49. Avatar Raelyn egolf says

    Ive had a fever of 104.4 since yesterday, it been going up nd down cause ive been takeing ibuprofen and asprin every 4 hrs. But i have a cough and sore throat also and dizzyness and headache as well. Idk what to do. The doctore told me i had a virus but i feel like its more then a virus. Please help!

  50. I’ve had a fever on and off for 2 days … Not more than 102 … average is like 99 .. I have a slight cough and some throat soreness … No other symptoms … I am normally very healthy … I can’t figure out why I have a fever ?

  51. This was incredibly helpful, I have had a fever of 101 for two days and now it’s up to 102, I have a bit of a cough (not a bad one)but my lungs almost feel heavy and laying down causes me to cough more. I am also diabetic. So if my fever doesn’t break in a today I think I may need to go to the hospital.

  52. Thank you for this very informative information on adult fever. I truly can’t remember the last time I had a 103 temp! I’m 55 and planing a first time trip with my daughter to Europe in two weeks hope this builds my immune system . It’s going on day 2 I feel aweful

  53. Avatar Steven Levine says

    At the moment, my temperature is 101.9 degrees. If not for the fever, I’d say I just have the symptoms of a very bad cold. Occasional coughing, preceded by a sore throat, the urge to lie in bed all day, and no appetite. Can a cold give a fever like that?

    (I think I do know exactly what brought the illness on.)

  54. Avatar Media Partners says

    Just because you don’t have insurance, doesn’t mean you can’t see a doctor. They will take cash.

  55. last night i had 106.2 fever. i have no health insurance so i couldnt go to the doctor and my car is also broken down. today, all day i have had a SEVERE headache and have been weak and dizzy.
    its nice to know that a fever so high was dangerous and there was nothing i could have done about it.

  56. I had a fever of 103. I have the stomach bug. I have had it for 4 days. Is that bad?

  57. I had a high fever with body temperature of 38.8 degree celcius last night at my brother’s New Year’s Eve party..

    I was shivering & had a terrible headache.. I had dry coughing too and vomitting a lot.. My body is aching all over but I still dare not go see any doctor because I had bad experiences..

    These tips really helps.. Thanks..

    Appreciates it..

  58. Avatar Media Partners says


    Glad it was helpful for you. Hopefully, nothing serious sent you searching.

  59. Thank you for your information on fever in adults.

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