Body & health

Menstruation

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Not yet reviewed by a clinician. This health entry was written from the public-health sources listed below and is general information only. It is not medical advice.

Definition

Menstruation, or having a period, is the monthly shedding of the uterine lining through the vagina when a pregnancy has not occurred.

At a glance

  • Menstruation is the shedding of the uterine lining through the vagina when there is no pregnancy.
  • A period typically lasts about 2 to 7 days and comes roughly every 21 to 35 days.
  • Cycles are often irregular in the first years after periods start and in the years before menopause.
  • Pads, tampons, menstrual cups, discs and period underwear are all options for managing a period.
  • Very heavy bleeding, bleeding between periods or after sex, or disruptive pain are worth discussing with a doctor.

In detail

A period typically lasts between about 2 and 7 days and happens roughly every 21 to 35 days, though cycles are often irregular in the first years after periods start and in the years before menopause. Blood loss is usually a few tablespoons in total, and cramps, bloating and tiredness are common.

Periods can be managed with pads, tampons, menstrual cups, period underwear or discs. Very heavy bleeding, periods that suddenly stop, bleeding between periods or after sex, or pain that interferes with daily life are worth discussing with a doctor, as they can point to conditions such as endometriosis or fibroids.

In a sentence

  • She keeps a spare pad in her bag in case her period starts at school.
  • The doctor asked when her last menstruation began and how long it usually lasts.

Where the word comes from

From Latin menstruus, meaning monthly, from mensis, month.

Not to be confused with

  • Breakthrough bleeding

    Breakthrough bleeding is unplanned bleeding between periods, often linked to hormonal contraception.

Common questions

How long is a normal period?

A period typically lasts between about 2 and 7 days and comes roughly every 21 to 35 days. Cycles are often irregular in the first years after periods start and in the years before menopause. Big changes in your usual pattern are worth mentioning to a doctor.

When is period pain or bleeding a reason to see a doctor?

Very heavy bleeding, periods that suddenly stop, bleeding between periods or after sex, and pain that interferes with daily life are all good reasons to see a doctor. These can point to conditions such as endometriosis or fibroids, which can be treated.

Related terms

Sources

  1. NHSPeriods
  2. MedlinePlusMenstruation
  3. ACOGYour First Period