Fasting is usually required for kidney function tests. Kidney function test usually refers to intravenous blood test for urea, creatinine, uric acid, cystatin C, etc. Diet will have a greater impact on urea and creatinine, especially for patients who eat more meat, which may lead to higher urea and creatinine, therefore, fasting is usually required before the test. Furthermore, drinking a lot of water before the test will cause blood dilution, which may also lead to test errors. If patients eat a lot of greasy food before the test, it may cause the blood to be transiently coeliac, and the test cannot be performed at this time. In summary checking renal function usually requires fasting, fasting is defined as abstaining from water and food for more than 8 hours. If the patient has hypertension, diabetes and other chronic diseases, need to take medication regularly for a long time, the patient can use a small amount of warm water to deliver the medication, at this time the impact on the test is smaller. It is recommended that the renal function test to regular hospitals, follow the doctor’s instructions to improve the relevant tests.