Does body temperature change? Can your temperature be less than 98.6 Degrees?

Normal human body temperature used to be defined by just one number 98.6 degrees Fahrenheit. But now medical experts say that a range of numbers can be considered normal body temperatures for healthy individuals.

Researchers have found that the “normal temperature” for adults can range from 98.2 degrees Fahrenheit to 99.9 degrees Fahrenheit (that’s 36.8 degrees Celsius to 37.7 degrees Celsius). That’s good news for worrywarts and bad news for children hoping that a thermometer reading of 99 degrees is a get-out-of-school-free-card.

So what is normal body temperature? A nineteenth-century German doctor by the name of Carl Wunderlich is responsible for designating 98.6 as normal temperature. He studied the body temperature of 25,000 adults, took 1 million temperature readings, and determined that the body temperature averaged 98.6 among people in good health.

We now know that many factors can affect the number that shows up on a thermometer. Your temperature changes throughout the day; it’s usually lower in the morning and higher in the evening. Eating, drinking, exercising, and taking a hot shower can all skew a body temperature reading if it’s taken just after those activities. Women’s body temperatures fluctuate during the menstrual cycle and ovulation. People who have a higher metabolic rate often will have a higher body temperature than those with slower metabolisms. And, like everything else in our bodies, our core temperature can change as we age. One study found that seniors have a lower average thermometer reading than younger adults.

How your temperature is measured and what kind of thermometer is used also can make a difference in the number that pops up. Most adults prefer to take their temperature orally by putting a thermometer under the tongue for a few minutes. In the doctor’s office, a tympanic ear probe is often the thermometer of choice. Temperature readings can also be taken by placing a thermometer under the arm, called an axillary reading, or in the rectum. Any of these methods can give an accurate measurement, and different body sites will yield different results. An axillary reading, for example, can be a full degree lower than a reading taken from the ear.

In the past, medical thermometers were made of glass and filled with mercury. Today there are many more choices with better technology, such as digital electronic thermometers, mercury free oral thermometers, and infrared ear thermometers.

Our body temperature is an important reading. It’s one of the vital signs, along with pulse rate, breathing rate, and blood pressure, that give doctors an overview of how a patient is doing. If any one of those readings is off, it’s going to be a signal that something is awry.

A fever can occur for many reasons, most commonly when the body is fighting an infection. A doctor should be consulted when a baby’s temperature is above 100 degrees Fahrenheit ( 37.8 degrees Celsius). Most pediatricians want to see any child who seems to be under the weather and is running a fever. In adults, fevers usually are evaluated in the context of other symptoms, such as headache, sore throat, cough, or chills. If a fever persists, it’s a good idea to call your doctor. If you’re curious about what your normal core body temperature is, try this: on a day when you are healthy, take your temperature several times to get a baseline. But wait at least 30 minutes after eating or drinking, exercising, or bathing to get an accurate reading.

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