Dysfunctional Uterine Bleeding (DUB): This is the most common cause of increased menstrual bleeding, often related to hormonal imbalances, particularly anovulatory cycles, which can lead to irregular and heavy bleeding.

Uterine Fibroids: These are common benign tumors that can cause heavy or prolonged menstrual bleeding due to their location and effect on the uterine lining.
Endometrial Hyperplasia: A condition where the lining of the uterus grows too thick, which can lead to heavy or irregular menstrual bleeding.
Adenomyosis: A condition where tissue similar to the lining inside the uterus is found outside its normal location, leading to heavy and painful periods.
Intrauterine Devices (IUDs): Certain types of IUDs, especially those that do not contain hormones, can cause increased menstrual bleeding as a side effect.

Cancer of the Uterus or Cervix: Although less common, these conditions can present with increased menstrual bleeding and are critical to diagnose early for effective treatment.
Bleeding Disorders: Conditions like von Willebrand disease can lead to increased menstrual bleeding due to difficulties in blood clotting.
Thyroid Disorders: Both hypothyroidism and hyperthyroidism can affect menstrual regularity and heaviness.
Pregnancy Complications: Ectopic pregnancy or miscarriage can present with abnormal vaginal bleeding.

Uterine Arteriovenous Malformations: Rare vascular anomalies that can cause significant bleeding.
Uterine Polyps: Growths in the lining of the uterus that can cause heavy bleeding.
Systemic Diseases: Certain systemic diseases, such as liver or kidney disease, can affect clotting factors or hormone metabolism, leading to increased menstrual bleeding.
Medication Side Effects: Certain medications, including anticoagulants, can increase the risk of heavy menstrual bleeding.