What is Basal Body Temperature?
Basal body temperature (BBT) is the temperature your body becomes during sleep. It can be determined by taking your temperature immediately after waking up in the morning using a basal body thermometer, and should follow these parameters:
- Daily, at the same time every morning, +/- one hour
- Taken consistently, the earlier the better (5-8am)
- After deep sleep
- Before getting up out of bed to use the bathroom, communicating, any physical contact, etc.
- Taken under the tongue
How does it work?
In a healthy menstrual cycle, basal body temperatures will cluster into two sections: The first clear distinction of lower temperatures (before ovulation), and the second clear distinction of higher temperatures (once ovulation is confirmed).
Lower temperatures (typically ranging from 97.0-97.7 F/ 36.11-36.50 C) begin during the onset of the follicular phase, on cycle day 1 (menstruation), and end at the day of ovulation. The number of days in this phase determines the length of our entire cycles, as it carries the most fluctuation in response to stress, alcohol, sleep alterations, travel, etc.
Once ovulation has occurred, BBT will rise (typically ranging from 97.7-98.3 F/ 36.50-36.83 C) for an approximate and stable 12-16 days until your next period (this chunk of time is called your luteal phase).
Find a caring fertility awareness instructor to learn the rules of the basal body temperature method.
How Much Does a BBT Cost?
Basal body thermometers range from $9 – $40. Choose from a list of favorites here.
What Are The Side Effects?
You will not get any side effects by using the basal body temperature method.
How Effective Is it?
99.7% Effective with perfect use, .3% Failure rate
97% Effective with typical use, 3% Failure rate
- Could support with getting pregnant
- Could support with preventing pregnancy
- Requires minimal daily attention
- Hormone free
- Promotes healthy body awareness, gaining self-confidence and self-responsibility
- Takes an initial time period to learn the method, as well as put it to practice (3 Months)
- Requires discipline and motivation to to chart regularly
- Requires correct and constant use for an effective outcome
- Does not prevent against HIV infection (AIDS) or any other sexually transmitted infections (STI’s)
Keep in Mind
- Temperature readings could be affected by fever, restless sleep, mouth breathing, varying work schedules, alcohol, medication etc.
- Do not use a fever thermometer or quick read thermometer. The thermometer needs to take 30 seconds to 1 minute to read an accurate temperature.
- PCOS (Polycystic Ovary Syndrome) or other hormonal irregularities commonly have “split peaks” where ovulation does not occur. These cycles become slightly confusing, because of the attempts for ovulation to take place. This happens when the body doesn’t produce quite enough estrogen in the follicular phase to trigger LH for ovulation to occur. Split peaks can be due to life’s positive/negative stressors, resulting in a longer follicular phase and ovulation to be pushed back.