Your kidneys help maintain normal blood concentration by removing wastes, excess fluid and electrolytes such as potassium. Potassium, blood urea nitrogen, or BUN, and creatinine blood tests can monitor kidney function in patients diagnosed with kidney disease. High levels of potassium in the blood, elevated BUN and elevated creatinine are all indicators of some degree of kidney dysfunction.
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The most common cause of high potassium in the blood, or hyperkalemia, is kidney disease, according to MedlinePlus.com. Most of the potassium in your body is found inside of your cells, although a small amount circulates throughout your body in your blood. A healthy blood potassium level falls between 3.6 and 4.8 milliequivalents per liter. Normally, your kidneys maintain tight control of the level of potassium in your blood by filtering excess potassium from the blood when needed. When your kidneys are not working properly, they do not remove potassium from the blood efficiently, causing levels to increase above 4.8 milliequivalents per liter.
When you eat protein, your body breaks it down into its building blocks, which are called amino acids. When protein is broken down, a waste product called nitrogen is produced in the liver. This nitrogen combines with other molecules to create another waste product called urea. Urea then enters the bloodstream where the kidneys remove it from the body through your urine. A healthy individual has very small amounts of urea in the blood. When the kidneys are not functioning properly, they do not remove urea, and levels accumulate in the blood. A blood urea nitrogen, or BUN, test measures the amount of urea in your blood. A healthy BUN usually falls between 7 and 20 milligrams per deciliter. If your BUN level exceeds 20 milligrams per decilliter, it can indicate kidney disease.
Your muscles use a compound called creatine in order to contract. Every time your muscles contract, creatine is broken down and a waste product called creatinine is produced. This creatinine enters your blood and travels to your kidneys, where almost all of it is removed by your kidneys. A normal blood creatinine level falls between 0.8 to 1.4 milligrams per deciliter. Elevated levels of creatinine in the blood indicate that the kidneys are not functioning normally.
Although potassium, BUN and creatinine tests can determine if your kidneys are not functioning normally, they cannot isolate the cause of the kidney dysfunction. Abnormal values can occur as a result of acute kidney failure, chronic kidney failure, glomerulonephritis and urinary tract obstruction. If your lab values come back abnormal, your doctor may recommend further testing to isolate the cause of your kidney disease.