Abnormal uterine bleeding is one of the commonest presentation of adolescent gynaecology in health care setting, predominantly due to anovulatory cycles. However, chronic anovulation with other risk factors such as unopposed oestrogen and obesity could lead to endometrial hyperplasia and carcinoma even in young women. We report a case of an adolescent with history of obesity and diabetes mellitus type II, who had heavy bleeding for 4 years eventually diagnosed with endometrial carcinoma. We discuss the presentation, histological finding and also primary care doctor’s role in identifying possible life-threatening cause of abnormal uterine bleeding in adolescents.