Basal Thermometer Vs. Body Thermometer

If you are trying to get pregnant, chances are a basal thermometer has been recommended to help you chart your cycle, determine ovulation and predict when you are most likely to conceive. A basal thermometer is more sensitive and more accurate than a regular thermometer, making it capable of tracking the minute changes in your basal body temperature that indicate changes in your cycle. Your basal body temperature is your healthy body's temperature immediately upon waking.

Function

• A basal thermometer measures your temperature to the nearest tenth of a degree, while a regular thermometer measures only to the nearest two-tenths of a degree. If your temperature is 98.44 on a basal thermometer, a regular thermometer will report only 98.4. The difference is small but key in charting basal body temperatures. A regular thermometer is often not sensitive enough to determine the slight changes in temperature that indicate ovulation.

Types

• There are two types of basal thermometers, digital and glass. Both can be inserted orally, rectally or, in the case of a woman charting her ovulation, vaginally. Digital basal thermometers are preferred because they offer results faster, and temperatures can be stored in the thermometer's memory.

  Regular electronic thermometers can be used in the mouth, rectum or armpit. The American Academy of Pediatrics recommends against using old-fashioned mercury-filled thermometers, because the glass can break, releasing poisonous mercury.

Benefits

• Basal thermometers are most often used by women who are attempting to become pregnant. Every basal thermometer set includes a basal body temperature graph to help you chart your basal body temperature and predict when you will be ovulating. To chart accurate temperatures, you need to take your temperature right when you wake up, at the same time every morning. If you are using a regular thermometer instead of a basal thermometer, you may not see any change in temperature throughout your cycle.

Expert Insight

• Broda O. Barnes, Ph.D., was the first to suggest using a basal thermometer to detect hypothyroidism in his 1976 book, "Hypothyroidism: The Unsuspected Illness." A pioneer in his field, Barnes pointed out that thyroid hormones are an integral part of cellular metabolism, so a low basal body temperature can be a symptom of reduced thyroid function. Barnes' work on this subject is still cited by many experts in the field of medicine.

Considerations

• When charting your basal body temperature, a basal thermometer is your best choice. To obtain accurate results, take your temperature at the same time and using the same insertion method each morning. A basal body temperature will be accurate only after a minimum of 3 hours sleep, preferably 5.