What are the possible causes of a sudden increase in menstrual bleeding?

Menorrhagia—abnormally heavy or prolonged menstrual bleeding—is a common gynecologic concern that can arise from a variety of structural, hormonal, systemic, or iatrogenic causes. Sudden onset of increased menstrual flow warrants prompt clinical evaluation to identify potentially treatable or serious underlying conditions.

Structural abnormalities are among the most frequent contributors. Uterine fibroids—particularly submucosal or intramural leiomyomas—can distort the endometrial cavity and impair normal uterine contractility, leading to excessive bleeding. Endometrial polyps, adenomyosis (ectopic endometrial tissue within the myometrium), and, less commonly, endometrial hyperplasia or malignancy (especially in women over 45 or with risk factors such as obesity, unopposed estrogen exposure, or PCOS) must be considered and ruled out with appropriate imaging (e.g., transvaginal ultrasound) and, when indicated, endometrial biopsy.

Hormonal imbalances are another major category. Anovulatory cycles—often seen in perimenopause, adolescence, or conditions like polycystic ovary syndrome (PCOS)—result in unopposed estrogen stimulation of the endometrium without the stabilizing effect of progesterone, causing irregular, heavy shedding. Thyroid dysfunction (especially hypothyroidism) and hyperprolactinemia can also disrupt hypothalamic-pituitary-ovarian axis regulation and contribute to menorrhagia.

Systemic disorders—including coagulopathies such as von Willebrand disease (the most common inherited bleeding disorder), platelet function defects, or thrombocytopenia—may present with menorrhagia as a primary symptom, particularly if there is a personal or family history of easy bruising, epistaxis, or prolonged bleeding after minor procedures. Chronic kidney disease and severe liver disease can likewise impair hemostasis.

Iatrogenic causes include anticoagulant therapy (e.g., warfarin, direct oral anticoagulants), antiplatelet agents (e.g., aspirin, clopidogrel), and certain intrauterine devices—most notably the non-hormonal copper IUD, which is associated with heavier menses in many users. Selective serotonin reuptake inhibitors (SSRIs) have also been linked to increased menstrual blood loss in some individuals.

A thorough evaluation should include a detailed menstrual history (onset, duration, volume, clots, intermenstrual bleeding), obstetric and gynecologic history, review of medications and supplements, assessment for signs of anemia or bleeding diathesis, and targeted laboratory testing (e.g., CBC, ferritin, TSH, coagulation studies if clinically indicated). Imaging and histologic sampling follow based on risk stratification and clinical suspicion. Early diagnosis and individualized management—ranging from hormonal therapy and tranexamic acid to surgical intervention—are essential to prevent complications such as iron-deficiency anemia and significantly improve quality of life.