Blood Cr means blood creatinine, and blood creatinine is one of the kidney function tests. The kidney function test includes several items such as blood uric acid, urea and creatinine. Elevated blood creatinine represents the decline of kidney function, and blood creatinine is actually the waste produced by human metabolism. Under normal circumstances, metabolic waste can be filtered through the kidneys and most of it is excreted with urine. When the kidney function decreases, blood creatinine will accumulate in the body beyond the normal range, and this time is called renal insufficiency. If the kidney function is particularly poor, the blood creatinine reaches a certain level, it is called uremia, generally the old standard is >707μmol/L is called uremia. The new standard is to determine the kidney function based on the value of blood creatinine, weight and age. If the kidney function is particularly poor, into the uremic uremic syndrome, may have to enter dialysis, that is, renal replacement therapy, using the machine to filter out the toxins in the body.