How to Take a Basal Temperature

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A mildly hypothyroid person can still appear to have normal thyroid lab results. The basal temperature test will give a good indication of thyroid problems but is not definitive. Use this as one more tool to recognize potential hypothyroidism.

How to Take a Basal Body Temperature

What is a basal body temperature?

The "basal body temperature" test was developed by Broda O. Barnes, M.D. Barnes developed and promoted a diagnostic test for thyroid function that became known as the "Barnes Basal Temperature Test". A mildly hypothyroid person can still appear to have normal thyroid lab results. The basal temperature test will give a good indication of thyroid problems but is not definitive. Use this as one more tool to recognize potential hypothyroidism.

Body temperature is very sensitive to hormone levels and may be higher or lower when a woman is ovulating or having her menstrual period.

How to take and record basal temperature

Use the same thermometer throughout the duration. An accurate thermometer is important. A fertility/basal thermometer, found at any pharmacy is the most accurate
If menstruating wait until the third day of onset before recording temperature. Menstruating can lower basal temperature to as low as 97.2 F
Immediately upon awakening, and with as little movement as possible, place the thermometer under the tongue or underarm.
Take temperature before eating, drinking or getting up to use the bathroom.
Take your temperature at the same time every morning
An armpit (axillary) temperature is usually 0.5°F (0.3°C) to 1°F (0.6°C) lower than an oral temperature.
Record the readings on three consecutive days at exactly the same time of day.
For a more accurate average many practitioners recommend recording temperatures for 10 days.
If the average temperature is less than 97.8 (oral) or 97.3 axillary (armpit) for three (preferable ten) consecutive days, then hypothyroidism is strongly suspected.

Factors affecting basal temperature

Other factors can affect body temperature, such as taking readings at different times, alcohol, illness, a restless night, and stress. Also do not use an electric blanket during the test. This can result in a higher than actual basal temperature.

Use the chart below to track your daily Basal Temperature:

Date	Basal Temperature	Notes

References:
https://www.webmd.com/infertility-and-reproduction/fertility-tests-for-women#3-7
https://en.wikipedia.org/wiki/Broda_Otto_Barnes