Overview

A period is the part of the menstrual cycle when a woman bleeds from her vagina for a few days.

For most women this happens every 28 days or so, but it's common for periods to be more or less frequent than this, ranging from day 21 to day 40 of their menstrual cycle.

Your period can last between 3 and 8 days, but it will usually last for about 5 days. The bleeding tends to be heaviest in the first 2 days.

When your period is at its heaviest, the blood will be red. On lighter days, it may be pink, brown or black.

You'll lose about 30 to 72ml (5 to 12 teaspoons) of blood during your period, although some women bleed more heavily than this.

Read more about heavy periods, period pain, irregular periods and stopped or missed periods.

When do periods start?

Periods usually begin at around the age of 12, although some girls will start them earlier or later.

A delay in starting periods isn't usually a cause for concern. Most girls will be having regular periods by age 16 to 18.

Sanitary products

Sanitary products soak up or collect the blood released during your period. The main types of sanitary products are:

• sanitary pads
• tampons
• menstrual cups

Sanitary pads

Sanitary pads are strips of padding that have a sticky side you attach to your underwear to hold them in place. One side of the pad is made of an absorbent material that soaks up the blood.

Pads come in many sizes, so you can choose one to suit how heavy or light your period is.

Pantyliners are a smaller and thinner type of sanitary pad that can be used on days when your period is very light.

Tampons

Tampons are small tubes of cotton wool that you insert into your vagina to soak up the blood before it comes out of your body.

There are 2 types of tampon - ones that come with an applicator and others without an applicator that you insert with your fingers. In both cases, there's a string at one end of the tampon, which you pull to remove it.

Tampons come with instructions that explain how to use them. If the tampon is inserted correctly, you should not be able to feel it inside you. If you can feel it or it hurts, it might not be in properly.

It is not possible for a tampon to get stuck or lost inside you. Your vagina holds it firmly in place and it expands inside you as it soaks up the blood.

Menstrual cups

Menstrual cups are an alternative to sanitary pads and tampons. The cup is made from silicone and you put it inside your vagina.

Menstrual cups collect the blood rather than absorb it. Unlike sanitary pads and tampons, which are thrown away after they've been used, you can wash menstrual cups and and use them again.

PMS (premenstrual syndrome)

Changes in your body's hormone levels before your period can cause physical and emotional changes.

This is known as PMS (premenstrual syndrome) or PMT (premenstrual tension).

There are many possible symptoms of PMS, but typical symptoms include:

• feeling bloated
• breast tenderness
• mood swings
• feeling irritable
• spotty skin or greasy hair
• loss of interest in sex

These symptoms usually improve when your period starts and disappear a few days afterwards. Not all women who have periods get PMS.

Getting pregnant

Working out when you can get pregnant – your fertile time – can be difficult. It's around the time you ovulate, which is about 12 to 14 days before the start of your next period.

But sperm can survive inside a woman's body for up to 7 days before ovulation occurs. This means your fertile time extends back earlier in your cycle.

You cannot get pregnant if you do not ovulate. Some hormonal methods of contraception, such as the contraceptive pill, contraceptive patch and contraceptive injection, work by preventing ovulation.

Changes in your periods

Your periods can change – for example, they may last longer or get lighter. This does not necessarily mean there's a problem, but it does need to be investigated.

You can see your GP, or visit your nearest women's clinic or contraceptive clinic.

Bleeding between periods, bleeding after having sex, or bleeding after the menopause needs to be checked by a doctor.

It might be caused by an infection, abnormalities in the neck of the womb (the cervix) or, in rare cases, it could be cancer.

You could be pregnant if you miss a period and you've had sex. See your GP if you've taken a pregnancy test and the result is negative (you're not pregnant) and you've missed 3 consecutive periods.

They will investigate the cause and recommend any necessary treatment.

When do periods stop?

Your periods will continue until you reach the menopause, which usually happens when you are in your late 40s to mid-50s. In the UK the average age of menopause is 51.

Your periods may start to become less frequent over a few months or years before stopping altogether. In some cases they can stop suddenly.

Delayed periods

Girls usually start their periods between 10 and 16 years of age. Most girls get their first period when they're around 12.

But everyone develops at different rates, so there's no right or wrong age to start having periods.

Your periods will start when your body is ready. This is usually about 2 years after the first signs of puberty appear. In girls, the first signs of puberty tend to be breasts beginning to develop and pubic hair starting to grow.

When to see your GP

See your GP if you have not started your periods by the time you're 16. Your GP can assess whether you're going through the normal stages of puberty.

It's also a good idea to see your GP if you have not developed any signs of puberty at all by the age of 14.

You may be advised to "wait and see". In many cases your periods will start naturally by the time you're 18.

Your GP may recommend having blood tests to check your hormone levels.

You may be referred to a specialist (usually a gynaecologist – a specialist in women's health). They'll try to establish the cause and will be able to recommend any appropriate treatment.

Possible causes of periods not starting

Possible causes of periods not starting include:

• a normal delay in development – this often runs in families, so if your mother or sister started her periods late, this may be why your first period is delayed
• a hormonal imbalance
• being underweight
• doing a lot of exercise – this can affect girls who do lots of athletics, gymnastics or dance
• eating disorders
• severe stress
• pregnancy – it's possible to get pregnant before you get your first period as your ovaries can start releasing eggs a few months before your periods start
• a problem with the ovaries, womb or vagina

Is there any treatment for periods that have not started?

It depends on what's causing the problem.

Hormone therapy may be recommended if the cause is a hormonal imbalance.

If the underlying cause is an eating disorder, treatment will often involve a combination of therapy and advice about your diet.

If doing a lot of exercise is thought to be the cause, you may be advised to do less and, if you're underweight, to increase your calorie intake.

If the underlying cause for your lack of periods cannot be treated, you should be able to get NHS therapy or counselling to help you come to terms with what this means for you.

Period problems

If problems with your periods are affecting your life, there's help and support available.

Before you see your GP about period problems, it can be useful to keep a diary of your symptoms throughout the menstrual cycle. This can give your doctor a detailed idea of what happens, and when, during your cycle.

Painful periods

Pain during periods is common. It's usually caused by the womb contracting to push out the blood.

Exercise may help relieve the pain, as well as taking over-the-counter painkillers, such as ibuprofen and aspirin.

However, do not don't take ibuprofen or aspirin if you have asthma or stomach, kidney or liver problems. Aspirin should not be taken by anyone under 16 years of age.

You could try paracetamol to relieve period pain, but studies have shown that it does not reduce pain as effectively as ibuprofen or aspirin.

Hormonal contraception (such as the contraceptive pill, the intrauterine system (IUS), the contraceptive patch or the contraceptive injection) can reduce period pain.

See your GP if the pain is so severe that it affects your daily life.

Read more about painful periods. 

Heavy periods

Some women naturally have heavier periods than others, but if your periods are so heavy that they impact your life, there is help available.

Talk to your GP about your bleeding, including how often you have to change your sanitary protection (towels, tampons or menstrual cup).

Your GP can investigate why you're experiencing heavy bleeding. These investigations may include a physical examination, blood tests or scans.

Treatments for heavy periods can include:

• some types of hormonal contraception, such as the intrauterine system (IUS) or the contraceptive pill
• tranexamic acid tablets
• anti-inflammatory painkillers, such as ibuprofen or mefenamic acid
• progestogen tablets
• surgery (depending on the cause)

Read more about heavy periods. 

Irregular periods

A period usually lasts 2 to 7 days, with the average period lasting 5 days.

The length of the menstrual cycle varies from woman to woman, but the average is to have periods every 28 days. Regular cycles that are longer or shorter than this, from 21 to 40 days, are normal.

But some women have an irregular menstrual cycle.

This is where there is a wide variation in:

• the time between your periods (they may arrive early or late)
• the amount of blood you lose (periods may be heavy or light)
• the number of days the period lasts

Irregular periods can be common during puberty and just before the menopause. Changing your method of contraception can also disturb your normal menstrual cycle.

Read more about irregular periods, including what causes them and when treatment may be necessary.

Stopped or missed periods

There are many reasons why you may miss your period, or why periods may stop altogether.

Some common reasons are:

• pregnancy
• stress
• sudden weight loss
• being overweight
• overexercising
• reaching the menopause

If your periods stop and you're concerned, see your GP.

Read more about stopped or missed periods.

PMS (premenstrual syndrome)

PMS is thought to be linked to changing levels of hormones throughout the menstrual cycle.

Not all women get PMS. If you do, the range and severity of symptoms can vary.

Symptoms may include:

• mood swings
• feeling depressed or irritable
• headaches
• tiredness
• bloating
• breast tenderness

Symptoms usually start and can intensify in the 2 weeks before your period, and then ease and disappear after your period starts.

Read more about PMS, including symptoms and treatment.

Endometriosis

Endometriosis is a condition where pieces of tissue similar to that which lines the womb (endometrium) grows outside the womb, such as in the ovaries and fallopian tubes.

Not all women have symptoms, but endometriosis can cause:

• painful, heavy or irregular periods
• pelvic pain
• pain during or after sex
• pain or discomfort when going to the toilet
• bleeding from your bottom
• feeling tired all the time

See your GP if you have symptoms of endometriosis, especially if they're having a big impact on your life.

Read more about endometriosis, including how it's diagnosed and treated.

Ovulation pain

Some women get a one-sided pain in their lower abdomen when they ovulate.

The pain can be a dull cramp or sharp and sudden. It can last just a few minutes or continue for 1 to 2 days. Some women notice a little vaginal bleeding when it happens.

Painful ovulation can usually be eased by simple remedies like soaking in a hot bath or taking an over-the-counter painkiller, such as paracetamol.

If you're in a lot of discomfort, see your GP about other treatment options.

Read more about ovulation pain.