Blood and urine tests may show if the kidneys are leaking abnormal amounts of protein waste; this possibly indicates failing kidney function, according to WebMD. Tests can be performed to check creatinine and blood urea nitrogen levels, which are strong indicators of kidney function.
Creatinine is a waste product made during the breakdown of food proteins, explains MedicineNet. It is produced from creatine, a molecule used for energy in building muscle. Normal levels of creatinine vary in individuals based on age and muscle development. Those with strong muscle development have more creatinine in the blood than people who suffer from malnutrition or chronic illness.
Common causes of elevated creatinine in the blood can often be attributed to diet and nutrition, medications or kidney infection. It is possible to treat and reverse elevated levels and to have high levels of creatinine without any symptoms of kidney disease. Possible symptoms of kidney failure often include fatigue, edema or swelling, dehydration and confusion, notes MedicineNet.
Blood urea nitrogen testing indicates how much nitrogen is in the blood and how well urea is being passed through the urine, states WebMD. Comparing blood urea nitrogen levels with creatinine levels may be a more precise indication of malfunctioning kidneys. Abnormal levels are also a common sign of dehydration, heart failure, prostate cancer and bacteremia in infants.