A period is when someone bleeds from their vagina. This is also called menstruation. They happen around every month as part of the menstrual cycle.

Every month or so, your body prepares itself for a possible pregnancy.

First, an egg is released from one of your ovaries and travels to your womb (uterus). The lining of your womb then thickens. This is so that the womb is ready for a baby if the egg gets fertilised by sperm.

If there is no sperm to fertilise the egg, the lining is not needed and is shed. The lining is made of blood and tissue and comes out through your vagina as period bleeding.

Periods usually start around the age of 12 but can begin earlier or later. You will likely have regular periods by the time you’re 16 to 18 years old.

Your periods will usually stop when you’re around your mid-40s to mid-50s. This is called the menopause. They can become less regular (more or less often), until they stop altogether.

How long does a period last?

Periods usually last for two to seven days. The bleeding is usually heaviest in the first two days.

You may hear that it’s 28 days from the first day of one period to the first day of the next. This is called the menstrual cycle. But this time, your cycle length, can be from 23 to 35 days.

What is period pain?

Your womb shrinks in and out (contracts) to push the womb lining out. This can cause discomfort and pain. This is often called cramps and is worse at the start. Over-the-counter pain killers, rest and a hot water bottle may help.

If the pain affects your day-to-day life in any way, or you struggle to manage it, see your GP. They may be able to help. They can also check for other conditions so you can get the right treatment

Conditions that can also cause pain include fibroids, pelvic inflammatory disease, adenomyosis and endometriosis.

What is premenstrual syndrome (PMS)?

Some people have physical and mental symptoms that vary during their menstrual cycle. This is known as premenstrual syndrome (PMS). Symptoms usually start a couple of weeks before your period. This is when your hormone levels change.

These symptoms can include:

• mood swings
• feeling depressed and irritable
• headaches
• tiredness
• tender breasts
• feeling bloated
• spotty skin
• greasy hair
• changes in appetite and sex drive

There is a severe form of PMS called premenstrual dysphoric disorder or PMDD. It causes intense symptoms that affect your mental health. They can make it difficult to work and lead a healthy life. Mind has more information about PMDD.

Coping with your periods and PMS

Period pain and other period problems can be hard to manage. Understandably, they can affect your mental and emotional health. Some things that might help include:

• regular exercise
• yoga or meditation to reduce stress
• eating a healthy, balanced diet
• not drinking too much alcohol
• if you smoke, getting help to quit
• a period tracker to help you understand your symptoms
• a hot bath or hot water bottle to ease pain
• over the counter painkillers like paracetamol or ibuprofen
• a TENS machine to help manage pain
• If symptoms carry on affecting your everyday life, talk to your GP.

What are irregular periods?

Irregular periods are when your cycle length is different from month to month.

Some common reasons for this include:

• the first year or two of your periods
• stress
• extreme weight loss or weight gain
• the perimenopause (the period before menopause)
• doing too much exercise
• ​​​polycystic ovary syndrome (PCOS) or other medical condition
• breastfeeding

In most cases irregular periods do not mean there is a medical problem. But talk to your doctor anyway. They will help find out if there’s a cause that can be treated. Keep a diary of the dates of your periods. This is so that you and your doctor can see if there is a pattern.

Contraception that uses hormones can affect your periods too, like the pill and implant. Bleeding on hormone contraception is withdrawal bleeding, not a period. So you do not need to worry if this is irregular. Withdrawal bleeding is also likely to be lighter than a period.

What can I do about heavy periods?

Heavy bleeding during your period can be uncomfortable and difficult to manage. If it’s affecting your life, talk to your doctor.

Keep track of how often you need to change your pad or tampon and how long the bleeding lasts. Your doctor might investigate why you’re having heavy periods. This might include an examination, scans, or blood tests.

There are treatments that can help heavy periods. These include tranexamic acid or hormonal contraception.

What can cause missed periods?

There are lots of things that can make you miss your period, aside from pregnancy. They include:

• stress
• sudden weight loss or being overweight
• doing intense exercise
• the contraceptive pill
• the menopause and perimenopause
• polycystic ovary syndrome (PCOS)
• breastfeeding

See your doctor if you have missed more than three periods in a row.

Changes in your periods

Any changes in your period should be checked out. If you notice your periods becoming shorter, heavier, or irregular, talk to your doctor.

You should see your doctor straightaway if you bleed:

• between periods
• after having sex
• after the menopause, whether you are taking hormone replacement therapy (HRT) or not.

This kind of bleeding might be caused by an infection or an injury to your vagina. In rare cases, it can be a sign of cancer. This sounds scary but there is usually no worrying cause. It’s just important to get checked out.

You can see your doctor or visit your nearest, sexual health clinic, women's health clinic or contraceptive clinic.

Impact of the Covid-19 vaccine on your periods

Your period following a vaccination for Covid-19 can be slightly delayed. Your periods should return to normal the following menstrual cycle.

Getting more support

Healthy Optimal Periods for Everyone (HOPE) is a website all about periods and menstrual health.

Watch our webinar series, Let’s Talk Periods, which explores common gynaecological conditions that can affect the menstrual cycle: endometriosis, fibroids, adenomyosis and PCOS. https://www.wellbeingofwomen.org.uk/what-we-do/campaigns/lets-talk-periods/

Our research on periods and menstrual health

As a women’s health charity, part of what we do is fund research to save and change the lives of women, girls and babies.