What happens when your period comes?

When your period comes, your body releases the lining of your uterus that it built up during the month, which comes out of your vagina as blood.

Basically, your body goes through a whole cycle powered by hormones. During the cycle, the inside of your uterus grows a soft, thick cushion. Near the end of the cycle, your hormone levels drop. Because your body doesn't need that lining right now, the cushion breaks down and leaves your body. The uterus is a muscle, and it squeezes to push out its lining. Those squeezes are what cause period cramps, so you might feel some aching in your lower tummy or lower back.

What it actually looks and feels like

• Blood comes out: It isn't a continuous rush, but more like a slow trickle or drips throughout the day. It can look bright red, dark red, or even brown.
• Cramps and aches: You might get cramps in your tummy, feel a bit bloated, or notice your lower back aching.
• Mood changes: Hormone changes before a period can make feelings bigger, though doctors aren't sure exactly how, so you might feel more tired, annoyed or emotional right before or during. If those feelings don't ease within a few days of your period starting, or they get in the way of school, friends or sleep, tell a grown-up.

To catch the blood, you use period products like pads or period underwear. Change your pad every 4 to 6 hours, sooner on heavy days.

Most people bleed for 3 to 7 days, and a first period can be much shorter and lighter. Tell a grown-up if you need a new pad or tampon every 1 to 2 hours, your period lasts more than 7 days, you pass clots bigger than about 2.5 cm, blood leaks through to your clothes or bed, you miss normal things because of your period, or you feel tired or out of breath a lot.

If you get cramps, there are medicines that help period pain, and a grown-up decides if you take one, which one and how much, for your age and weight. A heat pad, or a hot water bottle wrapped in a towel that a grown-up fills, can help too, and in a few small studies heat worked about as well as medicine. Tell a grown-up if the pain stops you doing normal things like school, doesn't get better with the pain relief a grown-up gives you, or keeps getting worse from one period to the next.