Hi,
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Prolonged and heavy periods, associated with clots and abdominal cramps could suggest chances of miscarriage/incomplete abortion if she had been sexually active without protection. It is difficult to comment on the exact cause without examining her and going ahead with further evaluation. Prolonged and heavy vaginal bleeding is not normal and should not be ignored. Further evaluation must be done to rule out chances of hormonal imbalances, thyroid abnormalities, anemia, bleeding disorder, vitamin deficiencies, probable ongoing miscarriage/incomplete abortion, endometrial hyperplasia, etc. She should consider visiting her doctor/gynecologist for examination and further evaluation to look for the underlying cause. Treatment as indicated (based on examination findings and investigations results) would be started to help her control the bleeding and regulate her periods. She should be in regular monitoring and follow-up with her treating doctor/gynecologist and report any new/abnormal symptoms immediately.
Take care.