Biphasic Pattern
A menstrual cycle in which ovulation occurs typically shows a clear and sustained thermal shift, which
continues throughout the luteal phase.
Progesterone is a heat producing hormone which is produced after ovulation and throughout the luteal
phase. This is what causes the temperatures to shift into a biphasic pattern and differentiates
between the pre and post ovulation temperatures. Ovulation occurs on the day before the sustained
temperature rise and cannot be confirmed until at least 3 temperatures are recorded which are higher
than your pre ovulation temperatures.
Temperatures may rise slowly, rise and fall (but stay above your pre ovulation temps) or rise sharply.
As ovulation cannot be confirmed until after the temperature shift, some women also use Ovulation
Predictor Kits (OPKs), which detect the surge of luteinizing hormone (LH) which occurs between 24-36
hours prior to ovulation.
Example of a biphasic pattern with a clear and sustained temperature shift after ovulation:
