Most women experience some form of period pain during their lifetime. The medical term for period pain is dysmenorrhoea.
Period pain is usually felt as painful muscle cramps in your lower tummy, which can sometimes spread to your back and thighs. Sometimes the pain comes in intense spasms, while at other times the pain may be dull but more constant.
The pain usually starts when your bleeding begins, and normally lasts for 12-24 hours.
Read more about the symptoms of painful periods.
Why it happens
Most cases of period pain occur when the muscular wall of the womb contracts. This compresses the blood vessels that line your womb, which temporarily cuts off the blood supply (and hence oxygen supply) to your womb. Without oxygen, the tissues in your womb release chemicals that trigger pain in your body.
Occasionally, period pain can be caused by an underlying medical condition such as endometriosis or pelvic inflammatory disease (see box, right).
Read more about the causes of painful periods.
How common is it?
Period pain is very common. Some studies suggest that approximately three quarters of young women and a quarter to a half of adult women experience pain and discomfort during their period. For up to one in five women, this pain is so severe that it stops them from doing their daily activities.
What to do
Most cases of period pain can be treated at home. You can buy a number of painkillers over the counter to help manage your pain.
Find out how you can manage period pain at home.
If your period pain is severe, visit your GP to check that no medical condition is causing your pain.
Read about the diagnosis of period pain caused by an underlying medical condition.