What is basal body temperature

Basal body temperature (BBT) means the body temperature measured in the morning before getting out of bed for exercise, eating, toileting or even before mood fluctuation after continuous sleep of more than 6-8 hours.

Why do we need to measure the BBT?

The BBT chart is used to see whether there are high and low­-temperature changes and the length of the high-temperature period. Progesterone is formed after ovulation, which stimulates the thermoregulatory center in the hypothalamus and releases norepinephrine to raise the body temperature by 0.3℃ - 0.5℃. The high temperature period will last until the next menstruation. The changes of high and low-temperatures during this period can be used as a reference for ovulation.

At the same time, the length of the luteal phase can be used to evaluate the function of the ovary. Generally speaking, as long as the high- temperature period is more than 11 days, it is normal ovarian function. If not, it may be luteal phase deficiency.

When is BBT most accurate?

Taking your BBT at the time when you have woken up is recommended, especially early in the morning for most people. However, people working night shifts can still take their BBT as long as they get 6-8 hours of sleep on a regular basis. 

Is it OK if I measure my BBT at different times each day? 

The measurement of the BBT should be continuous and must be carried out every day. If the BBT is not measured at the same time, it is easy to fluctuate greatly and affect its accuracy. The body temperature measured every day should be recorded and plotted into a coordinate chart. The chart and the degree of body temperature can determine the date of ovulation and the time of intercourse, so as to increase the chance of conception.

How long does it take to see the cycle?

You should begin to record your BBT from the first day of menstruation to the first day of the next menstruation. Although we can see the temperature change of the current period in each cycle, we suggest that you continue for more than three months to see the real physical condition. However, the BBT chart is a way to collect data and is a reference for physicians, not a medical practice, so problems with the chart are not something to be alarmed about.

Correct BBT method

• Step 1: go to the pharmacy and buy a BBT thermometer. Unlike regular household thermometers, it can display two decimal places. Even if the temperature rises only slightly, it can be measured accurately.
• Step 2: place the BBT thermometer beside the pillow before going to bed, and then wake up the next day. When you are not up and active (try to keep your body still in bed), measure it under the tongue. Wait for the beep, and keep it in the mouth for 3-5 more seconds for the temperature to stabilize. Read the temperature and record it on the chart, and connect today’s with yesterday's point.
• Step 3: measuring it within about one hour at the same time can get the most accurate results. For more than one hour, please indicate the measurement time in the remarks field. 
• Step 4: measure it continuously every day as much as possible. If there is a time difference or a cold, fever, intercourse and other conditions, they can be noted on the chart (leave the field blank for the day of not measuring).
• Step 5: in case of menstruation, please mark "X" on the remark field and one "X" represents one day of menstrual bleeding. Mark "○" to indicate intercourse. Mark "∆" to indicate menstrual pain. Mark "●" for fever. "□" indicates insomnia.
• Remember to bring the BBT chart with you on each return visit.