喵咪社区

It鈥檚 98.6 degrees Fahrenheit, right? Not necessarily, and here鈥檚 why that matters.

If you鈥檝e ever taken your temperature only to wonder if you鈥檙e cold-blooded after getting a low reading, it could be because the standard 98.6 degrees Fahrenheit is based on some very old research.

鈥淎 German physician came up with 98.6 degrees Fahrenheit, or 37 degrees Celsius, as the average human temperature, after obtaining millions of axillary (armpit) temperatures from 25,000 patients in 1851,鈥� says Rose Taroyan, MD, a family medicine physician with 喵咪社区.

Recently, the thinking on body temperature has changed a bit based on more current data. But in the age of COVID-19, in which is a main symptom, how does this shift affect how doctors determine a high body temperature? Let鈥檚 examine the evidence.

How normal temperatures for adults have changed

New data seem to point to temperatures trending downward in the last century and a half. One that looked at body temperatures since 1862 found a steady decline (a fraction of a degree) every decade, even when accounting for different methods of measuring temperatures. A recent large study found adults鈥� average temperature today to be 97.8 degrees Fahrenheit.

It seems like people鈥檚 bodies are actually less warm than they used to be. Doctors are now recognizing this variation in temperatures.

鈥淣ormal body temperature may be slightly higher or lower than 98.6 degrees Fahrenheit,鈥� Taroyan says. 鈥淔or a typical adult, body temperature can be anywhere from 97 to 99 degrees Fahrenheit.鈥�

What can influence your body temperature

Taroyan says that many factors can influence the average temperature range. For example, does body temperature change during the day? Yes, and it鈥檚 usually . 鈥淚t can also vary based on other factors like heavy clothing, physical activity, hot weather, warm foods and recent immunizations,鈥� she explains. In addition, a woman鈥檚 menstrual cycle may raise body temperature by 1 degree or more after ovulation.

Why a fever occurs in the body

When you鈥檙e sick, your body fights off infection, which raises your body temperature.

鈥淔ever is an inflammatory response 鈥� inflammatory proteins, called cytokines, trigger the hypothalamus in the brain to increase body temperature,鈥� Taroyan says. 鈥淏ut fever is not synonymous with infection, because it can be triggered by any inflammatory response.鈥�

This is why some autoimmune diseases, which cause inflammation, also sometimes cause fever.

Many conditions can cause a fever, such as:

• Viruses, like the flu or COVID-19
• Bacterial infections, such as urinary tract infections
• Autoimmune conditions, like rheumatoid arthritis and lupus
• Some cancers
• Some medicines or recent vaccines

So, what is considered a fever?

If body temperatures vary from person to person, do fevers, as well? The for a fever, Taroyan says, is 100.4 degrees Fahrenheit or 38 degrees Celsius. The Centers for Disease Control and Prevention does note, though, that number may not be the same for everyone and that a fever really means a person鈥檚 temperature is elevated beyond their norm.

Some has suggested that the threshold for a fever should actually be lower; the United States National Library of Medicine says an adult probably has a fever when the temperature is 99 to 99.5 degrees Fahrenheit or above. The starting point for fever in a child may also range from 99 degrees Fahrenheit (measured under the armpit) to 100.4 degrees Fahrenheit (measured rectally).

Given the wide range, how can you tell if you actually have a fever or not? You may have of a fever, such as feeling warm to the touch, feeling flushed or having the chills. If you鈥檙e familiar with your usual temperature (such as, if you take it daily at the same time, or have a fitness tracker that records your temperature), you may also be able to see your personal temperature baseline.

How to take your temperature

鈥淭here are many thermometers on the market today, each with pros and cons,鈥� according to Taroyan. 鈥淥ral, under-the-tongue thermometers take several minutes and may be altered by recently eating or drinking but otherwise can be fairly accurate,鈥� she says. Armpit thermometers also require several minutes and can be less accurate. Forehead thermometers are fast and easy but are expensive and error-prone, as are ear thermometers, which can even be affected by earwax.

Your choice may come down to personal preference, but Taroyan does recommend going digital. 鈥淒igital thermometers are the most accurate and fastest to use, however, they鈥檙e expensive,鈥� she says. 鈥淚f you鈥檙e unable to get a digital thermometer, the next recommendation would be a regular oral thermometer.鈥�

When to call the doctor

Taroyan says a fever is not a reason to rush to the doctor, generally speaking.

鈥淔ever by itself is not dangerous, until it reaches 106 degrees Fahrenheit,鈥� she says. 鈥淏ut, in the context of other neurological findings like lethargy, it requires an emergency visit.鈥�

She recommends scheduling an appointment with your doctor or visiting urgent care if:

• Your temperature is greater than or equal to
• You鈥檝e had a fever for more than three days.
• You have a fever with symptoms like throat-swelling, vomiting, headache, chest pain, stiff neck or rash.

If you are concerned you might have COVID-19, you can call your doctor to see if you should be tested. Although the range of coronavirus symptoms is wide, they include cough, shortness of breath, loss of taste or smell, congestion, nausea or vomiting. If you have emergency warning signs of COVID-19, such as trouble breathing, pressure in the chest, inability to stay awake, confusion or bluish lips or face, seek emergency care.

Virtual visits, also called telehealth, can be an easy way for your doctor to do an initial assessment of your fever and accompanying symptoms to see what further action you should take.

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