Stress induced hyperglycemia is the body's protect response against strong (patho-physiological and/or psychological) stress, sometimes the blood glucose level is too high due to out of the body's adjustment. Renal glucose threshold (about 9 mmol/L) is a window of glucose leak from capillary to interstitial tissue. It is important to keep blood glucose level < 9 mmol/L, for reducing vascular sclerosis as well as organs hypoperfusion, meanwhile pay attention to preventing more dangerous hypoglycemia. Glucose, as the main energy substrate, should be daily supply and its metabolism should be monitored. We used to talk "nutritional support". Support is conform the physiological ability of host, but therapy is to coordinate and change pathophysiology. So, nutritional support is not equal to nutritional therapy. For critical ill patients, we need to emphasize "nutritional therapy", i.e, do not give nutritional treatment without metabolic monitoring, make up for deficiencies and avoid metabolites overloading, rational adjustment to protect and coordinate organs function.