A basal thermometer measures basal body temperature (BBT), which is the lowest temperature of a person's body throughout the day. The basal thermometer is very sensitive to changes in temperature, and is often used by women who are trying to conceive.

Types

The basal thermometer is manufactured in both digital and glass forms, with the digital style being the most used. The digital-basal thermometer works faster than a typical glass thermometer, and some digital basal thermometers have the ability to store temperatures so you can record them later.

Basal vs. Fever

A basal thermometer is specifically designed to measure minute changes in body temperature, as small as .10 degree. A glass fever-measuring thermometer is, on the other hand, only accurate to .20 degree. A digital basal thermometer is also harder to break and therefore safer than a glass fever thermometer.

When to Use

If you are a woman trying to conceive, measure your temperature first thing in the morning, after at least three--but preferably five--hours of sleep. Take your temperature before you get up, eat or talk. Take your temperature at exactly the same time every day--even on weekends--and record the results on a chart (see Resources).

How to Use

The basal thermometer may be used orally, vaginally or rectally. If you are charting your BBT while trying to conceive, use the thermometer exactly the same way every time you measure your temperature.

What the Results Mean

A increase in body temperature of .40 to .70 degrees may signal that ovulation is occurring (the woman's body is creating a fertile environment for the egg that will be released during ovulation).

Warnings

If the basal thermometer shows no increase in temperature throughout your cycle--or if the increase lasts only a few days--see a doctor to evaluate possible problems.

Source:

StorkNet.com: The ABCs of Basal Body Temperature Charting

BabyHopes.com: Basal Thermometers: Tips for Use

UK Healthcare: Basal Body Temperature

Resource:

Free BBT Chart