Posted tagged ‘temperature’

98.6 is average, not normal: Dispelling fever fears

November 6, 2014

The Pediatric Insider

© 2014 Roy Benaroch, MD

What if I said 5’10” is the normal adult height for a male? Or a “B cup” is a normal bra size for a normal woman? Or that normal people have a skin tone the color of cappuccino, or that normal people should wear size 8 shoes? None of this makes sense. People come in all sorts of normal sizes and shapes, and almost all measurements of a person’s foot size or height or skin tone or whatever are going to be in a range of normal—from size 6 to size 13, or whatever.

It’s also wrong to say that a certain heart rate or blood pressure is normal. Your vital signs—pulse, respiratory rate, and blood pressure—vary throughout the day. There’s a range, not a single normal value. Likewise, your body temperature varies, usually falling into a range of normal values.

Normal temperatures vary from person to person, and by the time of day. Women tend to have slightly higher “normal temperatures” than men, and their measured temperatures can also change depending on their menstrual cycle. Bottom line: there isn’t a single, normal temperature for the human body.

The average human body temperature, overall, is probably something close to 98.6 degrees Fahrenheit. That means about half the time, your child will be a bit above that; at other times, below. A measured temperature above 98.6 does not mean your child is sick.

Since normal body temperatures follow a range of values, one accepted definition of fever is a temperature at or above 100.4 (some clinicians prefer 100.8). More important than the number, honestly, is how ill the child is acting and what other symptoms there are, but in any case a measured temperature less than 100.4 is not really a fever—it’s just a normal value in a normal range.

If your child has a measured temperature of 99.0 or 99.8, it’s not a low-grade fever. It’s not any kind of fever. It’s just a temperature in the range of normal, or maybe a temperature a little higher than average for that child. But it’s still not a fever. The child might still might be sick (depending on other symptoms), and might need comfort and reassurance–but don’t worry yourself or confuse the picture. A temperature in the normal range is not a fever.

More about fever in children:

What is fever?

Why do kids get fevers?

Don’t be afraid of fever

What to do when your child has a fever: The action plan

Should temperatures rise during sleep?

July 30, 2012

The Pediatric Insider

© 2012 Roy Benaroch, MD

“My son is 5 and he has no signs of being sick. But I have been noticing that his body is hot to the touch and his temperature is high (101 – 102) while he is sleeping. In the daytime he is usually around 98.6 or 99, but it worries me when he sleeps because it always goes high. Is this normal?”

Normal body temperature varies throughout the day. The lowest point is usually from 2-6 am, rising about 1 degree F through the day until a peak in the late afternoon. Measured temperature also varies with activity and ambient temperature, and can be influenced even by hunger and sleepiness.

It is a myth that 98.6 is “The Normal Temperature,” just like it would be a myth that 5’10” is “The Normal Height” for adult men. 98.6 is considered the middle of the range of normal, but even that isn’t very accurate, as different people will vary around their own “normals”. The 98.6 is more of historical interest than a medically exact measurement. It was figured out in the 19th century using thermometers that were incorrectly calibrated, and it’s actually wrong– but we’re kind of stuck with it now.

Since your son isn’t acting sick at all, why are you taking his temperature? An elevated measured body temperature can be a sign of illness, but really that’s only when a child is acting sick with symptoms. A measured temperature that’s higher than expected in a child who’s acting well and feeling well is probably just normal variation rather than a sign of disease.

If you’re worried, take him in for a good exam with his doctor, and bring your temperature logs. Write down the actual numbers from the thermometer, and write down how you measured them (what kind of thermometer). Don’t rely on ear temps or those skin-sensor devices, they don’t work to accurately measure temperatures.

More about fever:

What is it?

Why do kids run fevers

Dispelling fever phobia

The Fever Action Plan

Fever part 1: What is it?

June 1, 2009

The normal human body temperature is thought to average 98.6 F. We all remember this from elementary school, and I’ll bet many of you remember the old glass thermometers, the one your mom used with the little red line right at 98.6. If you could top that, you got to stay home! But, like so many things we were told in elementary school, the truth is more complex and murky.

The classic 98.6 is based on a book by Carl Reinhold (sometimes his name is given as “Carl Reinhold August Wunderlich,” a wonderful name that I hope comes up in casual conversation this week). In 1868 he published The Course of Temperature in Diseases, in which he hand-calculated the averages of about a million measurements in 25,000 patients, coming up with 37 C (=96.8 F). He also declared that based on his observations, 38 C (100.4 F) was the upper limit of the normal temperature, essentially defining “fever” for the first time. It turns out that his thermometers weren’t calibrated very well, and were probably off by at least 1 or 2 degrees, but he gave it a good try—especially considering that his thermometer was a foot long, and took twenty minutes to register a stable measurement. (I don’t know where he put that in his patients, and I’m not sure I want to know.) More recent research pegs the average temperature at 98.2 F, but even this varies at least one degree between individuals. One’s own temperature can also vary at least one degree based on the time of day (normal temperatures are lowest first thing in the morning, unless you’re ovulating.) There is also evidence that carefully measured temperature averages vary between human races and genders (women tend to run hotter than men—no surprise there.) Thought it’s not technically correct, 98.6 F (37 C) still remains widely accepted as the “normal” human body temperature for everyone at any time.

If 98.6 F is the traditional (though inexact) definition of “normal”, then what’s a fever? There isn’t a universal definition. Most pediatricians consider a rectal temperature above 100.4 to be a fever; in adults, the number 100 is more often used, usually referring to an oral temperature (though in the elderly, normal “resting” temperatures may considerably lower than 98.2 F). Measuring rectal temperatures becomes more difficult past a few months of life, so often an armpit, oral, or forehead temperature is measured. To be clear in communicating with your pediatrician, say the number that the device recorded, followed by the method you took it: “Junior was 100.8 degrees measured orally.” Don’t add or subtract degrees to “correct” the temperature, just tell us what the number is. In most cases outside of the newborn period, the exact number is not actually very important, but we do like to have a general idea of how high the fever was.

Fever occurs in children most commonly from infections, but can be a result of many other rarer problems (such as adverse reactions to medicines, inflammatory arthritis, cancer, and thyroid disease). Fever can also occur as part of “heat stroke,” when dehydration combined with exposure to heat overwhelms the body’s capacity to control its temperature. Victims of heat stroke feel warm and dry—not sweaty—and are often delirious or sleepy.  This is a true medical emergency that can lead to kidney failure, brain damage, and death. It’s the only health condition where fever itself contributes to harm.

This is the first post in a little series I’m writing on fevers. In future posts, we’ll explore what fevers are for, why parents don’t need to fear fevers, and a super-simple “pediatric insider” action plan for parents to follow when their child runs a fever. Stick around!