Menstrual cycle

The menstrual cycle is counted from the first day of full bleeding (cycle day 1) to the day before the next period starts. It has a follicular phase, in which follicles grow and the womb lining thickens, and a luteal phase after ovulation, in which progesterone prepares the lining for implantation. Cycles between about 21 and 35 days are generally considered regular; consistently shorter, longer or unpredictable cycles are worth discussing with a doctor.

Also known as: period cycle, monthly cycle

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.