This forms a bloody substance that passes through the neck of the womb (cervix) into the vagina for a few days.
Women use products such as sanitary pads, tampons or menstrual cups to collect the blood.
What is a ‘normal’ period?
Women usually bleed for four to eight days, and experience a period around every 28 days, but this varies from woman to woman.
Periods usually start at around the age of 12 but can begin earlier or later.
Women often lose between five and 12 teaspoons of blood during a period but some women lose more than this.
What other symptoms are there?
It’s normal for periods to be painful as the womb contracts to push out blood.
You can also experience physical and mental symptoms before it starts as your body’s hormone levels change. This is known as premenstrual syndrome (PMS).
These can include:
- mood swings
- tender breasts
- feeling bloated
- loss of interest in sex
- spotty skin or greasy hair.
Why have I missed a period?
There are lots of reasons a period can be late, or for your periods stopping entirely.
It’s important to keep in mind that menstrual cycles vary from person to person, and some women have irregular periods.
Here are some other reasons you might have missed a period, including:
- suddenly losing weight
- the menopause
- doing too much exercise
- polycystic ovary syndrome (PCOS)
- a medical condition
When should I talk to a GP?
You should talk to a GP if pain or other symptoms are severe enough to affect your everyday life.
If you think your periods are too heavy, or stop unexpectedly, you may want to visit a GP too.
Find more in-depth information about periods and sanitary products: