Basal body temperature

Basal body temperature (BBT) is taken immediately on waking, before getting up. Progesterone raises it by roughly 0.3 °C after ovulation, so a sustained rise suggests ovulation has already happened. BBT confirms ovulation in hindsight rather than predicting it, and illness, poor sleep or alcohol can distort the reading.

Also known as: BBT, temperature charting, temping

Last reviewed: 8 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.