Lactase, the intestinal enzyme that breaks down lactose, may momentarily stop being produced in young children who have acute diarrhoea, which is often brought on by infectious gastroenteritis. The primary sugar in milk, lactose, may not be digested as a result, which could make the diarrheal disease worse or last longer. However, it is unclear whether keeping young children away from lactose-containing milk or milk products speeds up their recovery from acute diarrhoea. Among India, diarrhoea is a leading cause of illness and mortality in children. Multiple risk factors, such as hunger, illness, a lack of sufficient medical treatment, and other variables including lactose intolerance, all contribute to higher mortality rates. There aren't many studies in India on lactose intolerance and severe diarrhoea. This study seeks to measure the prevalence of lactose intolerance in kids with severe diarrhoea and to evaluate the variables influencing the condition. In this prospective investigation, lactose intolerance was determined in 150 cases of acute diarrhoea based on stool pH (5.5) and the presence of reducing agents. Lactose intolerance was determined in 54 instances. When compared to lactose-tolerant patients, cases with lactose intolerance had lengthier hospital stays.