Some medical conditions that can cause long, heavy menstrual bleeding with clots include menorrhagia, uterine fibroids, hormonal imbalances such as menopause, and diseases affecting the uterus, such as endometriosis and adenomyosis, explains Mayo Clinic and WebMD. Thyroid problems can also lead to abnormal bleeding with clots, says Everyday Health and WebMD.
Menorrhagia refers to prolonged, heavy menstrual bleeding that can include passing clots beyond a single day, notes Mayo Clinic. Symptoms include bleeding that lasts more than a week. Certain conditions may cause menorrhagia, including malfunctioning ovaries, benign polyps and thyroid problems. Hormonal imbalances involving estrogen and progesterone can also result in heavy menstrual bleeding through the shedding of excess lining of the uterus.
Other specific conditions that can produce longer, heavier periods with clots are fibroids, obstruction of menstrual blood, an enlarged uterus due to pregnancy, and the uterine conditions of endometriosis and adenomyosis, says WebMD. When the tissue comprising the uterine lining grows outside of the uterus, it is endometriosis. When the same tissue grows within the muscle of the uterine walls, it is called adenomyosis. Pregnancy stretches the uterus, and if it does not regain its normal dimensions, menstrual blood can gather and clot before leaving the body.