You will want to take your temperature for four consecutive days, although some practitioners will tell you to take it for 14 consecutive days putting the thermometer under the left armpit for 7 days and the right armpit for the remaining 7 days.

If you are taking your Basal Metabolic Temperature for detecting ovulation and fertility, you will want to take it every day and chart the findings as the temperature will dip one whole degree approximately 24 hours prior to ovulation.

Take temperature at the same time every day before getting out of bed--even to urinate. For women still having their period, you will want to do the test starting the second day of menses because the hormone progesterone, released during certain other times of your cycle, will increase your body temperature. For men and post menopausal women take it for 4 consecutive days.

Before going to bed, shake the thermometer down to 96 degrees or less so you won't increase your basal temperature by doing that in the morning.

Before you even get out of bed to brush your teeth or start your day, place the basal thermometer into your mouth or under your arm for ten minutes.

Record the temperature. The normal basal temperature will be 97.8 to 98.2 degrees F

Repeat this test for four consecutive days or for however long your practitioner advises.

If your temperature averages at less than 96 degrees, this indicates low thyroid. Do not test when you have an infection or any other condition that would raise your body temperature.