Lo básico del ciclo

The four phases of your cycle

Revisado: 4 de octubre de 2026

Solo en inglés por ahora

Your cycle is often split into four phases: menstrual, follicular, ovulation and luteal. Here is what happens in each one, and why any phase dates you see are only estimates.

Four phases, two views

Doctors describe the cycle from two angles. The ovaries go through a follicular phase, while an egg ripens, and a luteal phase, after the egg is released. The lining of the womb (uterus) is shed during your period, then builds up, then gets ready for a possible pregnancy. Put together, the cycle is often described in four phases: menstrual, follicular, ovulation and luteal. The number of days in each phase differs between people and from one cycle to the next.

Menstrual phase: your period

The cycle starts on day 1, the first day of bleeding. Levels of the hormones oestrogen and progesterone are low, and this tells the body to shed the womb lining (endometrium) through the vagina. A period usually lasts 2 to 7 days, often about 5. Cramps are common, especially in the first days, because the muscle of the womb squeezes to push the lining out.

Follicular phase: building up

The follicular phase covers the time from the start of your period until ovulation, so it overlaps with your period. Follicle-stimulating hormone (FSH), made by a small gland at the base of the brain, makes several follicles grow. These are small sacs in the ovary, each holding an egg. The follicles make oestrogen, which rebuilds and thickens the womb lining once bleeding stops. The length of this phase can change from month to month, even in the same person.

Ovulation: the egg is released

When oestrogen gets high enough, the brain releases a surge of luteinising hormone (LH). This makes the leading follicle release its egg. Ovulation usually happens about 10 to 16 days before your next period. That is around day 14 in a 28-day cycle, but later in a longer cycle and earlier in a shorter one. Around this time, cervical mucus often becomes clear, wet and stretchy, and some people feel a twinge on one side of the lower tummy.

Luteal phase: ready, then resetting

After ovulation, the empty follicle becomes a small structure called the corpus luteum, which makes progesterone. Progesterone keeps the womb lining thick and ready for a fertilised egg to settle in. The luteal phase usually lasts about 10 to 16 days. If there is no pregnancy, the corpus luteum stops working, hormone levels drop, the lining breaks down and a new period starts. In the days before a period, some people notice bloating, sore breasts or mood changes.

Why the phases are only estimates

The phases and fertile window shown in Ciclo are estimates, and Ciclo is not contraception or a fertility test. A calendar cannot confirm whether or when you ovulated, because the day you ovulate can change from cycle to cycle. To avoid or plan a pregnancy, talk to a doctor, nurse or sexual-health clinic about reliable options.

This is general information. Phase timings differ for everyone, and estimated phases cannot confirm ovulation or prevent pregnancy.