Basal body temperature - meaning and definition
AlsoBBTresting body temperaturetemperature methodbasal temperatureBBT chartingtemping
Not yet reviewed by a clinician. This health entry was written from the public-health sources listed below and is general information only. It is not medical advice.
Definition
Basal body temperature is the body's temperature at complete rest, measured first thing in the morning, which rises slightly after ovulation.
At a glance
- It is the body's temperature at complete rest, measured first thing in the morning.
- It rises slightly after ovulation because of progesterone.
- It confirms ovulation only after it has happened.
- It is usually combined with other signs in fertility awareness.
- Illness, alcohol, poor sleep and shift work can all affect readings.
In detail
After an egg is released, progesterone causes a small but sustained rise of roughly 0.2 to 0.5 degrees Celsius. Charting it every day with a sensitive thermometer shows when ovulation has already happened, which is why it is used in fertility awareness methods and by people trying to conceive.
On its own it only confirms ovulation after the fact, so it is usually combined with other signs. Illness, alcohol, poor sleep and shift work can all shift readings.
In a sentence
- I take my basal body temperature before getting out of bed and note it in an app.
- Her chart showed a clear basal body temperature rise in the middle of the cycle.
Common questions
Can basal body temperature predict ovulation?
Not on its own. The temperature rise happens after an egg has been released, so it confirms ovulation after the fact. It is usually combined with other signs, such as cervical mucus.
What affects basal body temperature readings?
Illness, alcohol, poor sleep and shift work can all shift readings, which is why charting consistently at the same time each morning matters.
Related terms
Sources
- NHSNatural family planning (fertility awareness)
- Planned ParenthoodFertility Awareness Methods