The doctor will ask about your symptoms and medical history, and perform a physical exam. Tests may include:
Commonly Ordered Blood Tests—including complete blood count; calcium, phosphorus, and parathyroid hormone; and potassium levels
Blood Urea Nitrogen (BUN) and Creatinine—to see whether your kidneys are working properly. If they are not filtering the blood properly, the blood will contain excess amounts of creatinine and urea. Creatinine is a byproduct of muscle function, while urea is a waste product of protein metabolism.
Estimated Glomerular Filtration Rate—a measurement of how well the kidneys are processing wastes. Your doctor can calculate the GFR based on gender, age, body size, and blood creatinine level.
The formula used in clinical practice is called the Cockcroft-Gault equation:
Creatinine clearance or GFR (mL per minute) = (140 – age) X body weight in kilogram ÷ 72 X serum creatinine. If calculated for a female, this product is multiplied by 0.85.
The GFR determines the stage of chronic renal disease.
Glomerular Filtration Rate (GFR)
over 90 mL/min (normal)
60-89 mL/min (mild decrease)
30-59 mL/min (moderate decrease)
15-29 mL/min (severe decrease)
under 15 mL/min (kidney failure or end-stage renal disease)
Blood Electrolytes—The concentration of sodium, chloride, calcium, and potassium in the blood will be abnormal. Potassium, in particular, can quickly rise to dangerous levels.
Urine Tests—to see if the kidneys are working properly. If they are not working properly, your urine will contain protein. You may be asked to collect urine in a special container over a 24-hour period. This test will also show whether your kidneys are clearing creatinine at a normal rate. The amount of urine you produce is also significant. If your kidneys are failing—or starting to fail—you may produce little or no urine.
Kidney Biopsy—A small piece of kidney may be surgically removed and sent to a laboratory in order to try to ascertain the cause of kidney failure.
Johnson CA, Levey AS, Coresh J, et al. Clinical practice guidelines for chronic kidney disease in adults: Part II. Glomerular filtration rate, proteinuria and other markers.
Am Fam Phys.
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a