My daughter has to take painkillers during her periods — I'm worried she might have endometriosis

Dr Phil Kieran: "Endometriosis can be suspected based on symptoms and examination, but a definitive diagnosis is usually based on surgical inspection of the abdominal cavity and sampling of an area of endometrial tissue outside the uterus."
Painful periods are unfortunately very common with some studies suggesting it is present in up to 90% of women to some extent. The pain can be due to the normal functioning of the reproductive system, or it can be a sign that there is an underlying problem like endometriosis.