Some of the items that can be found out by drawing blood to check the kidneys include: 1. You can judge the kidney function, which refers to drawing blood to test the blood creatinine and urea nitrogen, which are metabolic wastes produced by the body, and should be excreted by the kidneys out of the body. If the indicators in the blood are elevated, it means that the excretory capacity of the kidneys is reduced, which is usually referred to as renal failure.2. Secondly, through the blood test, it is possible to determine the etiology of renal diseases, such as blood test for blood glucose, to see whether there is diabetes; the method of checking immunoglobulin and serum immune-fixed electrophoresis may determine whether the patient has multiple myeloma; some nephritic diseases can also be detected through the blood test to find clues. Some nephritic diseases can also be detected by blood tests.