Juvenile type 1 diabetes mellitus has an acute onset and is often triggered by infections or poor diet. Typical symptoms are excessive drinking, urination, food intake and weight loss (i.e., “three more and one less”). However, in infants, excessive drinking and urination are not easy to detect, and dehydration and ketoacidosis can occur very quickly. Prompt medical attention is recommended. In children, enuresis may occur because of increased nocturia. Elderly children may also experience a significant decline in physical fitness, such as lethargy, loss of energy and fatigue. 1. Three more and one less symptom: young diabetes mellitus early blood glucose rise, glucose in the urine increase leads to osmotic diuresis caused by increased urine volume, which leads to thirst, drinking, a large amount of glucose discharge caused by hunger, overeating, glucose utilization obstacles lead to fat decomposition for energy supply, resulting in emaciation. 2. Diabetic ketoacidosis: some patients are not diagnosed at an early stage, and diabetic ketoacidosis can be the first symptom, which manifests itself as deep and fast breathing, rotten apple smell, nausea, vomiting, and even consciousness disorder. People with the above symptoms should go to the hospital in time, under the guidance of the doctor to check and treat.