Medicines that increase the risk for accidental hypothermia include those used to treat anxiety, depression, or nausea, and some over-the-counter cold remedies. Ask your doctor how your medicines affect body heat.

Shivering increases muscle cell activity, which in turn produces heat. Severe shivering is one of the signs of hypothermia.

Other symptoms include shallow breathing; weak pulse; low blood pressure; a change in behavior during cold weather or a change in the way a person looks; excess shivering or no shivering; stiffness in the arms or legs; chilly rooms or other signs that the person has been in a cold place; poor control over body movements or slow reactions.

You should use a thermometer. If the person's temperature appears to be below 95 degrees F (35 degrees C), or you can't read it on an oral thermometer, take the person's temperature again using a rectal thermometer for a more exact reading. This should not be done outdoors. If the thermometer still does not show the temperature or is below 95 degrees F, call for emergency help. The only way to tell accurately if a person has hypothermia is to use a special thermometer that can read temperatures below 94 degrees F (34.4 degrees C). Most hospitals have these thermometers.

You can also use your own body heat to keep the person warm. Keep the person in the horizontal position. Lie close to the victim, but be gentle and do not handle the person roughly. Rubbing the person's arms and legs, as many rescuers are tempted to do, can make the problem worse as it may cause cool blood that had pooled in the extremities to return to the circulation and cause a further drop in core temperature. That is why rewarming of the trunk should be attempted before rewarming of the extremities.

Older people are at risk of hypothermia not only in cold weather, but in mildly cool temperatures as well. Older people may be vulnerable to hypothermia even when they live in nursing homes or group facilities. These institutions have to be careful when lowering temperatures, because patients who are already sick may have special difficulty keeping warm.

Illnesses that may blunt the response to cold include slow thyroid (hypothyroidism) or other disorders of the body's hormone system; stroke or other disorders that cause paralysis and reduce awareness; severe arthritis, diabetes, Parkinson disease, or other illnesses that limit activity; any condition that curbs the normal flow of blood; memory disorders.

Wind chill refers to the fact that brisk winds cause more rapid heat loss than calmer weather. Remember to listen to the weather report before venturing out in cold weather. Weather forecasters often suggest, even when the temperature itself is not very low, that the wind chill factor is low enough for people to stay indoors. Always dress for the weather and take extra layers if you have any doubts about the temperature or weather conditions.