The U24 5-HIAA test is advised in suspected carcinoid tumors involved in excess serotonin production. It aids healthcare professionals in evaluating symptomatic carcinoid syndrome presenting with diarrhoea, flushing, wheezing, and diagnosing gastrointestinal tract as well as bronchial carcinoid tumours. Elevated 5-HIAA levels at 48 hours provide better insights about increased serotonin production and metabolism, aiding in diagnosing and managing carcinoid tumors.