Blood concentration is usually caused by drinking less water or consuming too much water in the body, which is usually not a big problem, you can consider reviewing the situation after drinking more water, if it can be significantly reduced that is the problem of blood concentration. Then how to check? 1, hypertonic dehydration, the hypothalamic thirst center is stimulated, conscious people that have a sense of thirst and ask for water, at the same time, the anterior part of the hypothalamus optic suprachiasmatic nucleus is stimulated and the release of antidiuretic hormone, through the blood circulation and the action of the renal distal tubule and the collecting ducts, so the water back to the absorption increased, the amount of urine greatly reduced. After drinking water, less urine regulation of the body water back to normal, so hypertonic to isotonic, the total amount of body fluids are also restored, so mild dehydration, although often occurs, does not cause serious conditions; but if dehydration is serious, especially the regulatory malfunction is often presented with different degrees of symptoms. Hypertonic dehydration is often characterized by dry skin and mucous membranes, facial flushing and restlessness in addition to thirst. Children are prone to dehydration fever, decreased urine output and significant weight loss. Due to the drop in blood volume, blood pressure is significantly reduced, which can cause shock. And due to the insufficient amount of renal blood circulation, non-protein nitrogen and other metabolites are retained causing prerenal azotemia and acidosis. Dehydration of brain cells can cause psychoneurologic signs, and eventually coma can occur. At this time, the blood is concentrated, the number of blood cells, hemoglobin, hematocrit and blood Na+ can be elevated, and the plasma osmolality is also significantly higher than the normal high limit. Urine concentration and high specific gravity. 2, isotonic dehydration, thirst is often not obvious, hypotonic dehydration is no thirst, the patient in addition to the symptoms of the original disease, mainly with the lack of body fluids and sodium loss and other electrolyte and acid-base balance disorders. When dehydration exceeds 2%-3% of body weight, and blood Na+<125mmol/L, the patient will feel weak, limb weakness, dizziness, headache, mental lethargy, and sometimes nausea. When the loss of sodium (NaCl) per kilogram of body weight reaches 0.5-0.75g, blood volume often drops, blood pressure often decreases (systolic blood pressure <12kPa or less), pulse is thin and blurred vision. When sodium loss reaches 0.75-1.25 g per kilogram of body weight, there is apathy and apathy, rigor mortis, shock and coma, and there is often little (<10 mmol/L) or no sodium in the urine. Urine output may not be reduced in the early stages due to decreased plasma osmolality and suppression of antidiuretic hormone, but in the later stages, patients often die of dry peripheral circulatory failure. Blood Na+, Cl- is often reduced, but due to renal circulation disorders, non-protein nitrogen, creatinine, urea can also increase, the blood is also concentrated.