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Fever 101: What to Know About Thermometers

By November 19, 2021February 17th, 2022Expert Advice Well-being
Mother taking temperature and taking care of her sick son at home

Cold and flu season is here. This time of year can be tough for both adults and children, especially now as the common cold, flu, COVID-19, and other viruses are circulating simultaneously. While these viruses can cause uncomfortable symptoms, one symptom that is often concerning for many, especially parents, is a fever (a higher than normal body temperature).

If you’re concerned that you or someone in your family may be running a fever, the best way to confirm it is by taking their temperature. Let’s review some basics about thermometers and temperature readings.

There are several types of thermometers you can use to measure temperature safely and accurately at home including:

  • Digital thermometers. This type of thermometer uses electronic heat sensors to record body temperature. Digital thermometers provide the quickest and most accurate readings and can be used on children of all ages and adults. It can be used three different ways, including in the rectum, under the tongue, or under the arm, to get a temperature reading. Note: Don’t use the same thermometer to take temperatures by mouth and in the rectum.
  • Electronic ear thermometers. This type of thermometer measures the temperature inside of the eardrum and is appropriate for some infants (do not use on babies that are younger than six months old), toddlers and older children, and adults. While it is quick and easy to use, you must take care to use it properly by placing the tip correctly or the reading won’t be accurate. The accuracy of a reading can also be affected if there is too much earwax.
  • Forehead thermometers. This type of thermometer measures heat waves on the side of the forehead and can be used on children of any age and adults. While it is quick and non-invasive, forehead thermometers are considered less accurate than digital thermometers. Readings can be affected by direct sunlight, cold temperatures, a sweaty forehead, or holding the scanner too far away from the forehead.
  • Other types of thermometers, such as plastic strip thermometers, pacifier thermometers, smartphone temperature apps, and glass mercury thermometers, are not recommended.

Note: When using any thermometer, be sure to read the package instructions for proper use. For tips and more information on taking a temperature using any of the thermometers mentioned here, check out this video.

Don’t Fear the Fever

Once you have a temperature reading, here’s how to determine whether it’s normal or a fever.

  • For adults, a normal body temperature can range from 97°F to 99°F.
  • For babies and children, the normal range is anywhere between 97.9°F to 100.4°F.
  • Anything above 100.4°F is considered a fever.

But there’s no need to be worried right away when a fever is present. While a fever can be uncomfortable, it isn’t always a bad thing. It’s a sign that your body is doing its job — fighting an infection.

Most fevers go away on their own, and medication isn’t always needed. If a child or adult’s temperature is between 100 and 102°F, they generally feel OK, and are acting normally, they should drink plenty of fluids and rest. If a child or adult seems uncomfortable, over-the-counter medications may help lower a fever.

When to Call Your Doctor

While most fevers aren’t dangerous, you should seek medical advice in the following instances:


Toddlers/Older children

  • If a child of any age has a fever that rises above 104°F.
  • If your child refuses to drink, has a fever for more than two days, is getting sicker, or develops new symptoms, it’s time to call your pediatrician.
  • Go to the emergency room if your child has any of the following: a seizure, trouble breathing or swallowing, a stiff neck or headache, a sticky, dry mouth and has no tears with crying, is hard to wake up, or won’t stop crying.


Note: These are general guidelines. If you have any concerns about a fever regarding yourself or someone in your family, call your doctor.

Cleaning and Storing Your Thermometer

Once a fever has subsided, don’t forget about properly cleaning and storing your thermometer! Be sure to keep the instructions that came with your thermometer for specific cleaning and storage instructions. These general tips for maintaining your thermometer may also be helpful.

Dr. Francis Ferry

Dr. Francis Ferry has been a health plan Medical Director since 1995. He first came to Independence Blue Cross in 2001. A pediatrician by training, Dr. Ferry is a Clinical Associate Professor with the Rowan University School of Osteopathic Medicine. He also holds certifications as a Certified Physician Executive, a Certified Health Insurance Executive, a Certified Professional Coder, and a Senior Human Resources Professional. Dr. Ferry continues to work clinically as a pediatrician in office practice, hospital practice, and telemedicine.