Dysfunctional Uterine Bleeding (DUB): This is the most common cause of abnormal uterine bleeding, especially in the absence of other symptoms. It is often related to hormonal imbalances, particularly anovulatory cycles, which can lead to prolonged and irregular menstrual bleeding.

Hormonal Imbalance: Conditions such as polycystic ovary syndrome (PCOS), thyroid disorders, or hyperprolactinemia can lead to hormonal imbalances that cause prolonged menstrual bleeding.
Uterine Fibroids or Polyps: These growths can cause irregular and prolonged menstrual bleeding due to their location and effect on the uterine lining.
Intrauterine Device (IUD) Complications: Certain types of IUDs, especially those that release hormones, can cause changes in menstrual bleeding patterns, including prolonged bleeding.

Cancer (Endometrial, Cervical, or Uterine): Although less common, cancer must be considered in the differential diagnosis of prolonged menstrual bleeding, especially in older women or those with risk factors.
Pregnancy-Related Complications: Ectopic pregnancy or a molar pregnancy can present with abnormal vaginal bleeding and must be ruled out, especially if there is a possibility of pregnancy.
Bleeding Disorders (e.g., von Willebrand Disease): Underlying coagulopathies can exacerbate menstrual bleeding, making it heavier and longer-lasting.

Adenomyosis: A condition where tissue similar to the lining inside the uterus grows into the muscular walls of the uterus, potentially causing heavy and prolonged menstrual bleeding.
Uterine Arteriovenous Malformations: Rare vascular anomalies that can cause abnormal uterine bleeding due to the abnormal connection between arteries and veins.
Systemic Diseases (e.g., Liver or Kidney Disease): Certain systemic conditions can affect the coagulation system or hormone metabolism, leading to abnormal menstrual bleeding.