What Creatinine Tests Mean for Kidney Function

Creatinine is a waste product that is produced during protein breakdown. The creatinine blood test determines how much of this substance is in the blood. The results are used to determine how well a person's kidneys are functioning.

Indications

• The creatinine blood test is ordered when someone has signs and symptoms of kidney dysfunction. These indicators include fatigue, swelling, foamy urine, bloody urine, decreased urine output, flank pain, high blood pressure, urinary frequency and burning during urination.

Test

• Creatinine is usually tested as part of a basic metabolic panel (BMP) or comprehensive metabolic panel (CMP). The BMP also tests levels of glucose, sodium, calcium, potassium, carbon dioxide, blood urea nitrogen (BUN) and chloride in the blood. The CMP tests for the same substances as the BMP, with the addition of albumin, total protein, liver enzymes and bilirubin.

Problems

• Laboratory testing errors can result in inaccurate creatinine test results. False results can indicate kidney damage when none exists.

Results

• High creatinine levels indicate that the kidneys are unable to filter wastes as well as they should. This can occur as the result of kidney stones, trauma to the kidneys, kidney disease, kidney infections and kidney damage caused by medications or illegal drugs.

Additional Testing

• Urine testing for microalbumin and protein can support the results of a blood creatinine test or help doctors determine that kidney function is normal. When the kidney filters are damaged, microalbumin and protein are able to leak into the urine. If levels of these substances are high, kidney disease is indicated.