Menstruation is when the uterine lining sheds and fluid containing blood, vaginal fluid and tissue is excreted from the vagina. It is a normal monthly occurrence for women. 

Irregular menstruation is when the monthly cycle is off schedule and may be the result of certain medications, hormone imbalance, or underlying medical conditions. These include pelvic inflammatory diseases, endometriosis, or an inherited blood disorder. Benign or cancerous growths in the cervix, ovaries or uterus may also be the cause of irregular menstruation. 

Treatment of irregular menstruation will involve identifying the underlying cause of the changes to the cycle and addressing these. Drug classes commonly used to treat irregular menstruation are progestogens, and other infertility agents.