How Hypothermia Is Diagnosed

Hypothermia is both a medical condition as well as the description of an abnormal vital sign (low body temperature). In theory, diagnosing hypothermia should be fairly straightforward: Take a temperature and if it is below a defined threshold, the patient has hypothermia.

In reality, not all thermometers are the same and taking temperatures in different parts of the body will produce different values.

hypothermia diagnosis
Illustration by Joshua Seong. © Verywell, 2018. 

Why Diagnosis Is Important

Most people don't really think of mild hypothermia as being a medical condition that needs a diagnosis. Typically, we think of it as simply feeling too cold, in which case we take steps to avoid the discomfort associated with it—we go inside and turn up the heat, or put on a sweater and get a hot cup of cocoa.

It becomes more important to diagnose hypothermia when there is pressure to remain in the cold environment—someone who works outside or is injured, for example, can't escape the cold. 

Being able to clearly recognize hypothermia, however, means that the body's mechanisms to stay warm are not sufficient. A diagnosis gives the patient an opportunity to treat the hypothermia before it gets worse.

Stages

The body temperature will dictate the severity of the hypothermia.

Mild Hypothermia

This is the least dangerous stage of hypothermia and is defined as a core body temperature below 95 degrees. It comes with shivering, trouble concentrating, fumbling fingers, and discomfort.

Moderate Hypothermia

This stage is not as well defined as mild hypothermia, but is usually diagnosed as a core body temperature below 90 degrees and includes dilated pupils, confusion, fatigue, and eventually a loss of consciousness.

Severe Hypothermia

This stage entails s a core body temperature below 83 degrees and the patient is likely to be unconscious and completely unresponsive.

Obtaining Accurate Results

To truly diagnose hypothermia, an accurate body temperature reading is necessary. There are many ways to take a temperature. Unlike the pre-digital age, when the only thermometers were glass tubes containing toxic mercury, modern thermometers can take temperatures inside and outside the body. Some can take a temperature by barely touching the patient.

  • Forehead thermometers provide the simplest, accurate option. Their biggest drawback is that they are expensive.
  • Rectal thermometers are a bit faster and considered the most accurate at-home option for a thermometer. They are much more economical than a forehead thermometer.
  • Oral thermometers use essentially the same thermometer as a rectal temperature, but must be used properly to get an accurate reading. The accuracy of an oral temperature is not as good as that of a rectal temp. Using an oral thermometer and taking the temperature under the arm (axillary) is extremely inaccurate and not recommended.
  • Tympanic thermometers (in the ear) that can be obtained over the counter are fast but notoriously inaccurate. These do not make contact with the tympanic membrane like the professional versions do and require proper use to work correctly.

Differential Diagnoses

Hypothermia can mimic other medical conditions and those are best ruled out by a healthcare provider. Even shivering is not necessarily a sign of hypothermia. Fever and chills can cause shivering, as can withdrawal from opiate use.

The gold standard for hypothermia diagnosis is to use the core body temperature. If the patient is shivering and having difficulty with fine motor skills but doesn't have a body temperature below 95 degrees, it isn't hypothermia.

Likewise, if a patient is hypothermic with a body temp below 95 degrees and is unconscious, the diagnosis is hypothermia, but the patient could very easily have other conditions as well.

What to Do if You Think It's Hypothermia
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