Abnormal uterine bleeding is the medical term for abnormalities in the frequency, volume, duration, and regularity of the menstrual cycle. Abnormal uterine bleeding is classified using the acronym PALM-COEIN, with PALM representing the structural causes and COEIN indicating the non-structural causes. Etiologies include polyp (P), adenomyosis (A), leiomyoma (L), malignancy/hyperplasia (M), coagulopathy (C), ovulatory dysfunction (O); endometrial pathology including endometritis and atrophy (E), iatrogenic causes (I), and etiologies not otherwise classified (N). Diagnosis usually requires careful history-taking and examination, basic laboratory work, transvaginal ultrasound, and endometrial biopsy based on age and risk factors. Management depends on the underlying etiology, but often includes oral contraceptive pills, levonorgestrel-containing intrauterine devices, and surgery.