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At some point between the ages of 8 and 17, a girl will start to have periods. This is also known as menstruation. 

The average age to start is 12 but most people’s periods start between 8 and 17. Every month, the ovaries release an egg – this is called ovulation. If this egg is not fertilised by a sperm, it is shed through the vagina along with the lining of the womb, and this is what period blood is. A period will usually last for three to eight days.

The menstrual cycle

A menstrual cycle starts on the day that you get your period and lasts until the day before you get your next one. The average menstrual cycle is 28 days, but it can be a bit longer or shorter for some people.

When people talk about their period – they are usually referring to the bleeding which is the most visible part of the menstrual cycle, but it’s just one stage in a whole process that the body goes through every month in order to prepare for getting pregnant.

Every month, your womb or uterus (which is the space where a foetus (baby) develops) builds up its lining in order to prepare for getting pregnant. This lining, mostly made up of blood, is what is shed when your period starts. This is why your periods stop when you become pregnant – the womb lining is used to provide nutrients to the growing foetus, instead.


A woman’s ovaries release an egg (sometimes two) around 14 days after the first day of her period, or 10-16 days before the start of her next period. The egg travels down the fallopian tubes, which connect the ovaries to the womb. Once released, the egg lives for around 24 hours. If it is not fertilised, it is shed via a period, along with the womb lining.

How often periods happen

Most people who get periods have one every four to five weeks. You may like to keep a diary or use an app to track how often you get yours. Some people have regular periods, and can predict exactly when their next period is due. Other people have irregular periods, which mean they cannot predict when their next period is due. If you are worried about your periods, you can speak to a doctor or nurse.

It’s quite common for people’s periods to be irregular when they first start having them, then for them to become more regular as they get older.

Period blood

Period blood can be any colour from pink to red to brown. Sometimes period blood can be quite thick and other times it can be watery. This is all normal and you may notice your blood looks different at the start and end of your period. You may get blood clots, too – these are also perfectly normal and nothing to worry about, unless there’s a lot more of them than usual.

The blood that is shed during a period is usually around three to five tablespoons’ worth altogether, or around 50-90ml – though it sometimes feels like it’s more than that!

When you get a period, it’s normal for the bleeding to stop and start. For example, you may bleed for a few hours, and then stop bleeding for a few hours. Or you may stop bleeding all through the night, or all through one day, but then it will start again. Sometimes you’ll think it’s all over, then there’s one final wave. Everyone’s period is slightly different!

Sometimes, your period may be lighter than normal – sometimes it may be heavier than usual. Lots of things can affect how light or heavy a period is, so don’t worry too much if it changes from cycle to cycle! But if your period is significantly lighter or heavier than usual, for several cycles, you can ask a doctor or nurse for advice. And if you get a lot of pain during your period, make sure to tell a doctor, so you can get help.

The side effects of periods

One of the biggest effects of getting your period is called pre-menstrual syndrome or tension (PMS, PMT). You can start to experience the symptoms of PMS up to two weeks before you start your period. No one knows exactly what causes PMS, but it’s thought to be linked to changes in hormone levels caused by the menstrual cycle.

PMS can have different symptoms:


  • breast pain
  • cramps
  • muscle pain
  • spots
  • an upset stomach
  • diarrhoea or constipation


  • mood swings
  • feeling more irritable
  • having trouble concentrating
  • anxiety

You might have none, some, or all of these symptoms. Sometimes the symptoms last through your period, or you may find they disappear when you start to bleed.

Period products

Here’s a few options – you can mix and match, or just use one!


Tampons are small tubes of soft cotton which has been pressed together. They have a string attached to one end so you can pull them out after use. They can either come with an applicator (a plastic or cardboard tube used to help put them in), or without an applicator – make sure to check the box to see which kind it is. Tampons are inserted into your vagina, using either the applicator, or your fingers. It can be tricky to learn how to use tampons at first, but it gets easier with practice! They can be kept in for up to eight hours at a time and come in different sizes, from light to heavy flow, for different times during your period.

Tampons are invisible once they’re in, and their small size means they’re easy to keep in your bag or pocket until you need them. But sometimes people find them hard to put in (see the section below – I’ve tried to use tampons, but I can’t put one in.

How to insert a non-applicator tampon

How to insert an applicator tampon

Pads and liners

Pads (sanitary towels) are liners made of materials which soak up liquids, which you can use to line your knickers and ‘catch’ blood as it flows out. Like tampons, they come in a variety of different absorbencies – that is, some of them are designed for use when your period is really heavy, and some for when it’s lighter, like at the end of your period.

Pads can be simpler to use than tampons, as there’s no need to put anything into your vagina. But sometimes they can leak if your flow is really heavy, so make sure to change them regularly. You can’t use a pad if you go swimming, either.

With pads and tampons, make sure to go for unscented versions, as perfumes can irritate the sensitive skin of your vulva.

Both tampons and pads should not be disposed of in the toilet as they can cause blockages. Some toilets have special sanitary disposal bins, or you can wrap the tampon / pad in toilet paper and then put into the nearest bin available.

How to use a pad

Menstrual cups

Menstrual cups are small containers made of a flexible material like rubber or silicone, which – like a tampon – are inserted into the vagina to catch blood and stop it flowing out. Unlike tampons, they are reusable – you just empty the blood out of the cup, wash it, and reinsert it.

They’re good for environmentally conscious people as they involve less waste than tampons and pads, and you only need to buy one once, rather than getting new supplies for every cycle. But on the other hand, they can be difficult to learn to use, cleaning them in a public toilet (like at school or work) may be difficult or embarrassing, and they cost more money in one go than a packet of tampons or pads.

Period pants

Underwear or swimwear with a built-in absorbent layer. They can be washed and reused.

Period tracking

Period tracking is when you record information about your period to help you learn about and keep track of your menstrual cycle. People have been tracking their periods manually for thousands of years, but these days there are apps you can use to help track your menstrual cycle, such as Clue and Flo.

At its most basic level, period tracking can help you predict when your period is due, but there is more to your menstrual cycle than just your period. Tracking every day, or in the days before and after your period, can help you understand your cyclical symptoms.

The menopause

After several decades, your fertility (ability to have children) will fade away and eventually stop. At the same time, your periods will become irregular, then stop. This is called the menopause, and usually happens when someone gets to their mid to late 40s, but in rare cases it can happen at a younger age. If you’re worried, you can talk to your doctor or nurse.

Period FAQs

Go to our period FAQs page where we try and answer some of your biggest period worries.


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