Heavy periods are common in the teenage years. Many people don't realise theirs count as heavy, because they've never had anything to compare them with.
What counts as heavy?
Blood loss is hard to measure, so doctors use signs you can notice yourself. Your period may be heavy if:
you soak through a pad or tampon every one to two hours on your heaviest days
your period lasts longer than seven days
you pass clots bigger than a grape
you bleed through onto your clothes or sheets, or need a pad and a tampon at the same time
it stops you doing normal things, like going to school or training
Why it happens
In the first few years after your first period, many cycles happen without ovulation. Without enough of the hormone progesterone to keep it in check, the lining of the womb can build up more than usual, so there's more to shed. This is the most common reason for heavy periods in teenagers, and it can carry on for up to five years.
Sometimes heavy periods are caused by a bleeding disorder, where your blood doesn't clot as well as it should. The most common one is von Willebrand disease. Around 1 in 3 teenagers who see a specialist about heavy periods turn out to have a bleeding disorder. These conditions run in families, so it's worth asking whether women in your family have heavy periods or bleed a lot after dental work.
Is there a link with iron?
Every period, you lose some iron with the blood. Iron is a mineral your body uses to carry oxygen around. If you lose more than you take in, your iron stores drop. This is called iron deficiency, and it can leave you tired and finding it hard to concentrate.
Girls with heavy periods are about twice as likely to have low iron stores as girls with normal periods. The risk is highest for those who also don't eat red meat.
Your iron stores can run low well before you become anaemic, which is when your blood can't carry enough oxygen. That means a normal blood count doesn't always mean your iron is fine. You can ask for your ferritin to be checked too. Ferritin is a blood test that shows how much iron your body has stored. Don't start iron tablets without a blood test first, as too much iron can be harmful.
When should you see a doctor?
Book an appointment if:
you have any of the heavy period signs above
you feel tired all the time or get out of breath easily
your periods have been heavy since your very first one
a bleeding disorder runs in your family
you bleed for a long time after a cut or dental work
Get help straight away if you're bleeding so heavily that you feel faint.