Harvard Men's Health Watch

When is body temperature too low?

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Q. I am 82 years old and in good health. At my regular doctor visits, my temperature has been around 96.5° F. Is that too low?

A. Normal body temperature is not a single number, but rather a range of temperatures. The average normal body temperature — measured using an oral thermometer, or now more commonly with an infrared thermometer passed across the forehead — is 98.6° F (37° C).

However, recent studies indicate that 98.2° F (36.8°C) is a more accurate average, and in older individuals it may be about 1°F lower. One small study even suggested that in healthy older patients, body temperature ranged from 94° F to 99.6° F, with an average of 97.7° F.

Several factors can lead to a lower body temperature in older people. For instance, as you age, you lose fat under the skin in your extremities and your skin becomes drier; both of these changes cause loss of body heat. Metabolism, which also generates heat, tends to slow as you age. Medications, including beta blockers and antipsychotic drugs, also may lower body temperature, as can an underactive thyroid gland.

Because of their lower baseline temperatures, older people need to be careful to avoid prolonged exposure to the cold, which may lead to hypothermia, which occurs when your body loses heat faster than it can produce it and causes a dangerously low body temperature. Also, they should pay extra attention to fevers. A fever of 99° F, which doesn’t sound high, can be serious in an older person whose normal baseline temperature is below 97° F.

— by William Kormos, M.D.Editor in Chief, Harvard Men’s Health Watch

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