High osmolality is divided into high blood osmolality or high urine osmolality, which has more causes, such as strenuous exercise, diabetes mellitus, low intake of water, cardiac insufficiency, renal failure, etc. 1. High blood osmolality: patients sweat more due to strenuous exercise, and timely supplementation of water will lead to high blood osmolality; the increase of glucose in the blood of diabetic patients will also lead to the phenomenon of high blood osmolality. Patients with high blood osmolality may have symptoms such as dehydration and shock. 2. High urine osmolality: patients due to low water intake, the body’s water reduction leads to urine concentration, which in turn leads to patients with high urine osmolality; and cardiac insufficiency, renal failure patients will appear high urine osmolality phenomenon. Patients with high urine osmolality may experience diarrhea, vomiting, and high fever. Patients with high blood/urine osmolality should go to the hospital in time if they experience any discomfort to avoid delaying their condition.