Learn about your menstrual cycle

A cycle can be divided into two main phases: the time from the start of a period until ovulation, and the time from ovulation until the next period. So a period is not the end of the cycle. It is day one of a new cycle.

The first day of actual menstrual bleeding is counted as day one. When pregnancy has not occurred, the levels of the hormones oestrogen and progesterone fall. Part of the lining inside the uterus then breaks down and leaves the body as menstrual bleeding.

While you are bleeding, the brain releases hormones including FSH. This causes several small follicles in the ovaries to begin developing. A follicle is a small fluid-filled sac containing an egg cell. Usually one eventually becomes the follicle that develops an egg towards ovulation.

The developing follicle produces increasing amounts of oestrogen. Oestrogen helps the lining of the uterus build up again. This part of the cycle is called the follicular phase and lasts from the start of your period until ovulation. It is often the part of the cycle that varies most in length.

The amount and consistency of vaginal discharge can change throughout the cycle. Around the time before ovulation, some people notice discharge that is clearer, more slippery or stretchy. Others notice almost no difference. Discharge alone cannot tell you with certainty which day you ovulate.

When oestrogen reaches a sufficiently high level, the brain responds with a rise in hormones including LH. This hormonal surge triggers ovulation: a mature egg is released from an ovary and picked up by the fallopian tube. Ovulation does not necessarily happen on day 14. Timing can vary both between people and from one cycle to another.

An egg can usually be fertilised for approximately the first 24 hours after ovulation. Sperm can survive in the body for several days. This means pregnancy can occur after sex several days before ovulation. It is one reason why counting calendar days or relying on so-called safe days is not a reliable contraceptive method.

After the egg is released, the follicle remaining in the ovary changes. It begins producing more progesterone as well as oestrogen. Progesterone helps maintain the uterine lining in case a fertilised egg implants. This phase is called the luteal phase.

If pregnancy does not occur, oestrogen and progesterone levels fall. The lining of the uterus then starts to break down. A new period begins, marking day one of the next cycle.

Around 28 days is often used as an example, but it is not a universal rule. In adults, approximately 25 to 35 days is considered common variation, while adolescents may have more irregular cycles during the first years after their first period. The time before ovulation can vary substantially. The time from ovulation to the next period is often more stable and is commonly around two weeks.

Some people notice changes in discharge, pain around ovulation, tender breasts, bloating, mood, sleep or energy. Others notice very little. There is no fixed set of symptoms you are supposed to experience in each phase, and research does not support the idea that everyone has a predictable 'super week' when their body or performance is always better.

Start by recording the first day of bleeding. You can also note how many days you bleed and one or two things you are curious about, such as pain, discharge, mood, sleep or energy. After a few cycles, you can look back and ask: Does this happen around the same time? Has anything changed? Does it affect my daily life?

Look at both the days when you have symptoms and the days when you feel well. If a headache occurs before your period several times, it may be a pattern worth discussing with a healthcare professional. If you feel tired all month, the conversation should also consider other possible explanations.

A relationship in timing alone does not show what causes a symptom. The goal is to make your experience easier to understand and find appropriate support, rather than force every day into a particular menstrual phase. You do not need complete tracking records before asking for an assessment.

An app or calendar can be useful for remembering what you record, such as the first day of bleeding or symptoms. It may calculate when your next period or ovulation is expected based on earlier cycles, but it cannot know with certainty when you actually ovulate. Predictions become especially uncertain when your cycle varies.

Hormonal contraception can affect or suppress ovulation and change when and how you bleed. Bleeding while using hormonal contraception is therefore not always a period that follows ovulation. If you use hormonal contraception, it may be more useful to learn how that particular method affects your body and bleeding pattern.

Talk with a school nurse, youth health clinic or doctor if period pain strongly affects your everyday life, you have very heavy or prolonged bleeding, your periods stop for a long time or your pattern changes noticeably, or you have recurring physical or emotional symptoms that are difficult to manage. You can also ask questions simply because you are unsure what is usual.