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Adult Symptoms > Fever Symptoms > Fever


  • Fever is the only symptom

Fever can be defined using one of the following measurements:

  • Oral temperature greater than 100.0° F (37.8° C)
  • Ear (tympanic) temperature greater than 100.4° F (38.0°C)
  • Rectal temperature greater than 100.4°F (38.0°C)
  • Forehead temperature strips are unreliable

General Information

  • In most clinical situations, fever does no major harm, and may actually benefit the human body by helping it to fight off infection. Nevertheless, fever is an abnormal finding. It can signal a serious illness, especially in adults who are old, frail, or have a weakened immune system.
  • Adults tend to run lower fevers than children. Fever may be further blunted or even absent in elderly patients.
  • Fever itself can cause muscle aches, nausea, lightheadedness, weakness and headache.

Normal Body Temperature

  • 98.6° F (37°C) is the oral temperature that most physicians, nurses, laypersons, and medical references state is "normal."
  • The average temperature of healthy elderly patients is the same as younger adults. However, there is some data to suggest that the average temperature in chronically ill elderly patients is lower than that of other healthy adults. Thus, interpretation of a temperature reading in a chronically ill elderly adult must be done with caution. Because lower baseline temperatures can be expected in this group of patients, it may be easy to miss a fever if the conventional fever definition is used.

Normal Variations in Body Temperature

  • There is a normal daily awake-sleep cycle variation in temperature, with the low occurring at 6 AM and the high occurring at 6 PM. The low and high temperatures vary by 0.9° F (0.6° C).
  • In women, temperature increases about 0.9° F (0.6° C) at the time of ovulation.
  • Temperature can go up in response to physical activity, particularly during hot weather.

See More Appropriate Topic (instead of this one) If

FIRST AID Advice for Shock: Lie down with the feet elevated.


Call 911 Now (you may need an ambulance) If

  • Difficult to awaken or acting confused
  • Very weak (can't stand)
  • Severe difficulty breathing (e.g., struggling for each breath, unable to speak)
  • Lips or face are blue
  • Rash with purple (blood-colored) spots or dots

Call Your Doctor Now (night or day) If

  • You feel weak or very sick
  • Fever of 103° F (39.4° C) or higher
  • Fever of 100.5° F (38.1° C) or higher and you:
    • Are over 60 years of age OR
    • Have diabetes mellitus or a weakened immune system (e.g., HIV positive, cancer chemotherapy, chronic steroid treatment, splenectomy) OR
    • Are bedridden (e.g., nursing home patient, stroke, chronic illness, recovering from surgery) OR
    • Are a transplant patient (e.g., liver, heart, lung, kidney)
  • Headache and stiff neck (can't touch chin to chest)
  • Difficulty breathing
  • Signs of dehydration (e.g., no urine in more than 12 hours, very dry mouth, lightheaded, etc.)
  • Have an intravenous catheter (e.g., central line, PICC, or peripheral intravenous line)

Call Your Doctor Within 24 Hours (between 9 am and 4 pm) If

  • You think you need to be seen
  • Fever of 100.5° F (38.1° C) or higher and you have traveled to a foreign country in the last month
  • Fever present for more than 3 days

Call Your Doctor During Weekday Office Hours If

  • You have other questions or concerns

Self Care at Home If

  • Fever with no signs of serious infection and you don't think you need to be seen


  1. Reassurance: The presence of a fever usually means that you have an infection. Most fevers are good and help the body fight infection. The goal of fever therapy is to bring the fever down to a comfortable level. Use the following definitions to help put the level of fever into proper perspective:
    • 100-102° F (37.8 - 38.9° C): Low-grade fevers and may help body fight infection.
    • 102-104° F (38.9 - 40° C): Moderate-grade fevers; cause discomfort.
    • Over 104° F (over 40° C): High fevers; cause discomfort, weakness, headache, lethargy.
    • Over 107° F (over 41.7° C): The fever itself can be harmful.
  2. For All Fevers:
    • Drink cold fluids orally to prevent dehydration (Reason: good hydration replaces sweat and improves heat loss via skin). Adults should drink 6-8 glasses of water daily.
    • Dress in one layer of lightweight clothing and sleep with one light blanket.
    • For fevers 100-101° F (37.8-38.3° C), this is the only treatment and fever medicine is unnecessary.
  3. Fever Medicines:
    • For fevers above 101° F (38.3° C) take acetaminophen or ibuprofen.
    • The goal of fever therapy is to bring the fever down to a comfortable level. Remember that fever medicine usually lowers fever 2 degrees F (1 - 1 1/2 degrees C).
    Acetaminophen (e.g., Tylenol):
    • Take 650 mg by mouth every 4-6 hours. Each Regular Strength Tylenol pill has 325 mg of acetaminophen.
    • Another choice is to take 1,000 mg every 8 hours. Each Extra Strength Tylenol pill has 500 mg of acetaminophen.
    • The most you should take each day is 3,000 mg.
    Ibuprofen (e.g., Motrin, Advil):
    • Take 400 mg by mouth every 6 hours.
    • Another choice is to take 600 mg by mouth every 8 hours.
    • Use the lowest amount that makes your pain feel better.
    Extra Notes:
    • Acetaminophen is thought to be safer than ibuprofen in people over 65 years old. Acetaminophen is in many OTC and prescription medicines. It might be in more than one medicine that you are taking. You need to be careful and not take an overdose. An acetaminophen overdose can hurt the liver.
    • CAUTION: Do not take acetaminophen if you have liver disease.
    • CAUTION: Do not take ibuprofen if you have stomach problems, kidney disease, are pregnant, or have been told by your doctor to avoid this type of anti-inflammatory drug. Do not take ibuprofen for more than 7 days without consulting your doctor.
    • Before taking any medicine, read all the instructions on the package.
  4. Lukewarm Shower for Reducing Fever: Take the fever medicine first. Take a lukewarm shower or bath for 10 minutes. Lukewarm water should be warm enough that it does not make you shiver, but cold enough that it helps cool you off and reduce your temperature. Do not sponge yourself with rubbing alcohol.
  5. Expected Course: Most fevers from a viral illness such as a cold fluctuate between 99.5 and 103° F (37.5 - 39.5° C) and last for 2 or 3 days.
  6. Contagiousness: You can return to work or school after the fever is gone.
  7. Call Your Doctor If:
    • Fever lasts longer than 3 days (72 hours)
    • You become worse

And remember, contact your doctor if you develop any of the "Call Your Doctor" symptoms.

Disclaimer: This information is not intended be a substitute for professional medical advice. It is provided for educational purposes only. You assume full responsibility for how you choose to use this information.

Author and Senior Reviewer: David A. Thompson, M.D.

Last Reviewed: 9/15/2011

Last Revised: 11/20/2011

Content Set: Adult HouseCalls Symptom Checker

Copyright 2000-2012. Self Care Decisions LLC; LMS, Inc.

Additional Resources:

 How to use the Adult Health Topics pages
 When to call the doctor
 Reviewers of Clinical Content

Disclaimer: The information contained in these topics is not intended nor implied to be a substitute for professional medical advice, it is provided for educational purposes only. You assume full responsibility for how you choose to use this information.

Always seek the advice of your physician or other qualified healthcare provider before starting any new treatment or discontinuing an existing treatment. Talk with your healthcare provider about any questions you may have regarding a medical condition. Nothing contained in these topics is intended to be for medical diagnosis or treatment.

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