Bleeding for a month or longer, often described as prolonged or excessive, requires medical attention. This condition is formally known as menorrhagia or classified as Abnormal Uterine Bleeding (AUB). A typical menstrual period lasts no more than seven days; bleeding that significantly exceeds this duration suggests an underlying issue with cycle regulation. This article provides an overview of potential causes but is not a substitute for professional medical diagnosis.
Hormonal Fluctuations and Endocrine Factors
The menstrual cycle is a tightly controlled process orchestrated by the Hypothalamic-Pituitary-Ovarian (HPO) axis, and disruptions to this system are a frequent cause of extended bleeding. When ovulation does not occur—a condition called anovulation—the ovaries fail to produce progesterone, the hormone responsible for stabilizing the uterine lining. This absence of progesterone allows estrogen to continue stimulating the endometrium, causing it to build up excessively.
The resulting lining becomes structurally unstable and sheds in an unpredictable, heavy, and extended manner, which is a common pattern in abnormal uterine bleeding. Anovulation is commonly observed at both extremes of the reproductive spectrum, such as in adolescence when the HPO axis is still maturing and during the perimenopausal transition. During perimenopause, the natural decline in ovarian function leads to erratic hormone levels, resulting in unpredictable cycle length and flow.
Systemic conditions that affect the endocrine system also interfere with the HPO axis. Polycystic Ovary Syndrome (PCOS) is a common example, where hormonal irregularities prevent regular ovulation and cause the unopposed estrogen effect. Thyroid dysfunction, whether underactive (hypothyroidism) or overactive (hyperthyroidism), can likewise disrupt the balance of reproductive hormones. External stressors like rapid weight changes, extreme exercise, or psychological stress can lead to a temporary anovulatory state and subsequent irregular bleeding.
Structural Changes in the Uterus and Cervix
Beyond hormonal imbalances, physical changes and growths within the reproductive organs can mechanically or structurally interfere with the normal process of uterine lining shedding and blood clotting. Uterine fibroids, which are benign muscle tumors of the uterine wall, are a frequent cause of heavy and prolonged flow. These growths can distort the uterine cavity, preventing the uterus from contracting effectively to stop bleeding, and may also increase the local growth of blood vessels.
Fibroids located just beneath the lining of the uterus are particularly prone to causing severe bleeding due to their proximity to the endometrial layer. Similarly, endometrial polyps, which are localized overgrowths of the uterine lining tissue, contain abnormal microvasculature that is fragile and prone to bleeding. The presence of polyps can also hinder the complete shedding of the uterine lining, leading to extended bleeding.
Another structural condition is adenomyosis, where the tissue that normally lines the uterus grows into the muscular wall. This infiltration causes the uterine wall to thicken and become less pliable, compromising the muscle’s ability to contract and clamp down on blood vessels during menstruation.
Inflammation or infection of the cervix or endometrium, such as Pelvic Inflammatory Disease (PID) or cervicitis, can cause persistent irritation and abnormal vessel fragility. These conditions cause the tissue to be easily damaged, resulting in continuous or intermittent bleeding that extends beyond a normal cycle length.
Impact of Contraception and Medications
External agents, particularly certain types of contraception and medications, represent a distinct category of causes for prolonged bleeding. Intrauterine Devices (IUDs) can significantly alter bleeding patterns. The copper IUD is known to increase both the volume and duration of menstrual bleeding, often by impairing the body’s ability to clot blood in the uterus.
In contrast, hormonal IUDs, which release a progestin, may initially cause irregular bleeding or persistent spotting for the first three to six months after insertion. This is due to the progestin thinning the uterine lining, which can result in unpredictable, intermittent shedding. For both types of IUDs, the presence of the device itself can sometimes cause a local inflammatory response.
Changes in systemic hormonal contraception, such as starting, stopping, or inconsistently using birth control pills, patches, or injections, can also lead to breakthrough bleeding or a prolonged period. The sudden fluctuation or withdrawal of synthetic hormones destabilizes the uterine lining, triggering premature or extended shedding. Certain non-hormonal medications, most notably anticoagulant drugs prescribed for cardiovascular conditions, can also directly affect the body’s entire clotting system, turning a normal menstrual period into a prolonged and heavier bleeding event.
When Prolonged Bleeding Requires Immediate Attention
While many causes of prolonged bleeding are not medical emergencies, certain signs indicate that the blood loss is severe or represents an acute complication demanding immediate medical evaluation. A flow that is heavy enough to soak through one or more sanitary pads or tampons every hour for several hours in a row is considered a sign of excessive blood loss. Passing blood clots that are larger than a quarter also signals that the body’s natural clotting mechanisms cannot keep up with the rate of bleeding.
Ongoing heavy bleeding can quickly lead to anemia, a condition where the body lacks enough healthy red blood cells to carry adequate oxygen to tissues. Symptoms of anemia include persistent fatigue, unusual weakness, paleness, or shortness of breath, which develop as the body attempts to compensate for the reduced oxygen-carrying capacity. These symptoms, alongside heavy bleeding, require prompt testing to check iron levels and blood count.
Prolonged bleeding can also be the first symptom of a serious complication related to pregnancy, such as an early miscarriage or an ectopic pregnancy. A positive pregnancy test combined with continuous bleeding is an urgent matter that necessitates immediate medical assessment. While rare, conditions like undiagnosed bleeding disorders or endometrial cancer must be systematically ruled out, especially in individuals with risk factors. If you experience any of these severe symptoms or if the bleeding significantly impacts your daily life, scheduling an appointment with a healthcare provider is the necessary next step.