The renal function four items may be different in each hospital. The basic renal function three items are blood creatinine, urea nitrogen and uric acid, some hospitals add serum β2-microglobulin and count it as renal function four items, and some hospitals may add blood glucose to get renal function four items, so there is a difference in the cost of the test, which fluctuates between 40-100 dollars. Kidney function test requires patients to fast, and it is recommended that patients have a light diet for 3 days before. The kidney function four items can be checked through blood sampling to clarify whether the patient has kidney failure or not. For example, in renal failure, serum β2-microglobulin, creatinine, urea nitrogen, and uric acid will be elevated. If there is no problem with the four renal function tests, it does not mean that the patient’s kidneys are not damaged at all, because in the early stage of renal damage, the patient may not have renal failure and the elevation of the above indexes.