Abnormally heavy or prolonged menstrual bleeding can have many causes. Possible causes of menorrhagia fall into three categories; uterine-related problems, hormone-related problems, and other illnesses or disorders.

The possible causes include:

• Uterine fibroids: These noncancerous tumors grow either inside or outside the uterine wall. They can cause heavy bleeding or painful periods.
• Uterine polyps: Polyps are overgrowths of endometrial tissue, which is the type of tissue that lines the inside of the uterus.
• Irregular ovulation: If hormonal disruptions cause irregular ovulation, the lining of the uterus can build up and become too thick. When this lining eventually sheds during menstruation, heavy bleeding can occur. This is common during puberty and perimenopause. It can sometimes occur due to weight loss or stress or as a symptom of certain medical conditions, including polycystic ovary syndrome (PCOS) and hypothyroidism.
• Adenomyosis: In people with this condition, tissue from the lining of the uterus becomes embedded in the muscle of the uterus. It can cause painful and heavy menstrual bleeding.
• Nonhormonal intrauterine device (IUD): This type of birth control device sits in the uterus and can cause heavy bleeding.
• Pelvic inflammatory disease (PID): This infection of the reproductive organs often results from untreated sexually transmitted diseases.
• Pregnancy-related complications: Pregnancy-related problems, such as pregnancy loss or an ectopic pregnancy, can cause abnormal bleeding.
• Cancer: Uterine, cervical, and ovarian cancers affect the reproductive system and cause heavy bleeding.
• Inherited bleeding disorders: Examples include Von Willebrand’s disease and platelet function disorders.
• Medications: Certain anti-inflammatory and anticoagulant drugs can lead to heavy bleeding.

Other health conditions that can cause menorrhagia include thyroid disorders, endometriosis, and liver or kidney disease.