Kidney Function Test Abnormal Labs mainly look at urea nitrogen, creatinine, cystatin C, uric acid, urinary protein, red blood cells and so on. Creatinine and urea nitrogen are products of muscle and protein metabolism in human body. If there is a general elevation of creatinine and urea nitrogen, it often indicates kidney injury. If urea nitrogen is elevated, it may be caused by physiological factors such as infection, fever, large intake of high protein foods or high catabolism, or it may be caused by kidney diseases such as various types of glomerulonephritis. For example, an elevated creatinine may be caused by physiological factors such as strenuous exercise or consumption of large amounts of meat, or by renal diseases such as various types of glomerulonephritis. Cystatin C reflects the glomerular filtration rate changes in the indicators, such as elevated can suggest that there are different degrees of renal damage, but should also be combined with other relevant indicators, such as creatinine, urea nitrogen, urine routine and so on. Uric acid is the product of purine metabolism in the body, such as diet too much high purine food, can appear high uric acid; such as dietary improvements in uric acid is still elevated, or may suggest that the kidney function decline, but should also be combined with other renal function test indicators. In the early stage of kidney injury, creatinine will not be increased, the main manifestation of urine protein, urine red blood cells increased, urine specific gravity decreased and so on. Elevation of one index alone is not necessarily caused by kidney injury, especially slightly higher or lower than normal value, it may be a normal fluctuation. It is necessary for the doctor to make a comprehensive judgment based on the patient’s symptoms, past history and all the laboratory tests.