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Week 1: Basal Body Temperature Monitoring

September 8, 2011

Basal body temperature is the lowest temperature attained by the body during rest (usually during sleep). It is generally measured immediately after awakening and before any physical activity has been undertaken, although the temperature measured at that time is somewhat higher than the true basal body temperature (see Fig. 1). In women, ovulation causes an increase of one-half to one degree Fahrenheit (one-quarter to one-half degree Celsius) in basal body temperature (BBT); monitoring of BBTs is one way of estimating the day of ovulation. The tendency of a woman to have lower temperatures before ovulation, and higher temperatures afterwards, is known as a biphasic pattern.

Example of a basal body temperature chart. Menstruation begins on day 1. The rise in themperature between days 14 and 18 are the indication of ovulation. Temperature was taken orally with a regular fever thermometer

Most women track basal body temperature (BBT) to find out when they are fertile or not (for either trying to conceive or preventing to conceive).

During the first two weeks of a woman’s cycle, her body temperature is lower (97.0 to 97.5 F), due to the presence of estrogen. With ovulation, a rise in body temperature takes place – caused by an increase of the hormone progesterone – in order to provide a warmer, more fertile environment. A minimum temperature rise of 0.4 to 0.6 degrees F can be measured – and this change will last through the duration of the menstrual cycle. By monitoring when this temperature change takes place, you can estimate when ovulation has taken place.

Some medical practitioners mistakenly or brazenly diagnose hypothyrodism using BBT, when is not accurate. I also believe that women take accountability for their own health by tracking their own BBT months before going to a doctor when they suspect thyroid issues or any other disease concerning the adrenal/endocrine system. Sometimes we also make an unrealistic expectation that our doctors can make accurate diagnostics with just one visit and with just occular inspection.

Our doctors should act as a consultant, in the end we still make the decision for ourselves. We also help the doctor gather as much data about ourselves.

To measure your BBT, use an older oral glass/Mercury thermometer, or a special BBT thermometer available at some pharmacies. For glass thermometers, shake it down before going to bed, and leave it close by and within reach. As soon as you awake, with minimal movement, put the thermometer in your armpit, next to the skin, and leave it for ten minutes. Record the readings for three to five consecutive days. Women who still have their menstrual period should not test on the first five days of their period but can begin on day 5. Men, and girls and women who are not menstruating can test any time of the month.

Here is the chart of my BBT for one week (starting on Day 2 of my menstruation up to Day 9). Note that my BBT is lower on Day 5 and is lower than 97.6 F (36.2 C)— almost similar to the example BBT chart above.

If the average BBT is below 97.6 Fahrenheit, some complementary practitioners would consider a diagnosis of an underfunctioning thyroid or insufficient thyroid hormone replacement. An average BBT between 97.8 and 98.2 is considered normal. Temperatures from 97.6 to 98.0 degrees Fahrenheit are considered evidence of possible hypothyroidism, and temperatures less than 97.6 degrees can be even more indicative of hypothyroidism. Some practitioners, however, consider any temperature under 98 degrees to be indicative of hypothyroidism.

However, even if BBT is measured after day 5 of the menstrual cycle, it is still probably not enough to rule out or confirm a thyroid issue. Our temperature is normally low when we are at rest. In the middle of the day, our body temperature rise with every increase of activity. Thus, I think an average of the body temperatures taken at least 3-4 times a day is more accurate. I also believe that our metabolism plays a role in this fluctuating temperature.
Starting today, I will be measuring my temperature 4 times a day,
1. BBT – upon waking up
2. then every after 3 hours
will create a separate blog entry about Metabolic Temperature monitoring next week.
Read more about metabolic temperature here.

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