Thirst may occur in the early stages of diabetes. Diabetes mellitus is a group of metabolic diseases characterized by chronic hyperglycemia due to multiple etiologies, caused by defects in insulin secretion and/or action, and its typical symptoms are “three more and one less”, i.e., polyuria, polydipsia, polyphagia and weight loss. The cause of thirst is the increase in plasma osmolality due to the increase in blood glucose and the osmotic diuresis that takes away water. Patients with the above symptoms can monitor their own blood glucose. Diabetes can be diagnosed if fasting blood glucose ≥7.0 mmol/L, or 2-hour post glycemic load blood glucose ≥11.1 mmol/L, or random blood glucose ≥11.1 mmol/L, accompanied by the symptoms of the three polydipsia and one hypoglycemia (polydipsia, polyphagia, polyuria, and weight loss). If there is any discomfort, prompt medical attention is recommended.