A "normal" body temperature in a human registers at 98.6 degrees Fahrenheit. Like your weight, your body temperature fluctuates throughout the day. Sustained periods of time in which you run a fever, or a higher-than-normal temperature, can indicate illness. Subnormal temperatures may also be the sign of health problems.
One of the most obvious causes for a subnormal temperature is hypothermia. The condition, to which older people are more susceptible than younger adults and children, occurs when body temperature drops to 95 degrees Fahrenheit or lower. Hypothermia can occur when you have been exposed to extreme cold, after an injury when your body goes into shock, or as a result of hormone imbalances in which your body cannot regulate temperature effectively.
Hypothyroidism may also cause you to run a subnormal temperature. Your thyroid produces hormones that regulate a number of vital functions, including body temperature. An extreme form of hypothyroidism, a case in which your body does not produce enough thyroid hormone, is called myxedema. Myxedema is very dangerous and can interfere with breathing ability and oxygen levels if not treated. One of the signs of myxedema is a steady decrease in body temperature to subnormal levels. Intravenous delivery of thyroid hormones and steroids treats this form of hypothyroidism.
Running a subnormal temperature can indicate infection in your body, particularly in babies and small children. Although running a higher-than-normal temperature is a more common symptom of infection, Medline Plus explains that this is not always the case. Consult your doctor if you notice other symptoms of illness or infection, including a rash, sore throat or cough or irritability.
Running a subnormal temperature based on the widely accepted value of 98.6 degrees may mean nothing bad and is not always a source of concern. Although the normal body temperature of the majority of the general public may be 98.6 F, there is some variation among individuals, according to Columbia University Health Services. If you are not suffering from any other signs of infection or illness and your temperature is in the range of 96 to 97 degrees, your normal may just be lower than that of other people.