A typical period usually lasts for 5 days. During which, a woman loses around 30-40 ml of blood. Menorrhagia is defined as excessive menstrual bleeding. It is usually defined as period that last for more than 7 days, losing more than 80 ml of blood and passing large clots of blood. In some cases, Menorrhagia can indicate more serious gynaecological condition. In rarer cases, heavy periods can be caused by liver or kidney disease, blood clotting disorders, thyroid disorder, or gynaecological cancer. It is recommended that all sexually active women and women over the age of 21 have regular pelvic exams and Pap smear tests. However, you should seek medical advice whenever you experience heavy or irregular menstrual bleeding.