Early symptoms of diabetes mellitus mainly include: 1. slow and long duration, insidious onset, some patients are asymptomatic in the early stage; 2. typical symptoms are polyphagia, polyphagia, polyuria and wasting, i.e. three symptoms of polyphagia; 3. diabetes mellitus caused by acute complications, mainly manifests as ketoacidosis, patients are comatose, even delirium, deep and big breathing, accompanied by rotten apple smell; 4. most patients present themselves with chronic complications, manifesting as blurred vision, edema, numbness of limbs, itchy skin, etc.