What is the BUN to Creatinine ratio?

What is Blood urea nitrogen?

Blood urea nitrogen is a waste product formed during the process in which our bodies break down proteins. After a protein is deconstructed, the liver produces nitrogen-containing ammonia. The nitrogen reacts with other elements in our bodies (such as carbon, hydrogen, and oxygen) to form urea. Urea then travels through the liver and into the kidneys via the bloodstream. Healthy kidneys should filter out urea and other chemical waste products from the blood through urine. A blood urea nitrogen (BUN) test measures the amount of nitrogen in our blood that has been created by urea and is typically ordered to assess kidney function.  An unusually high BUN level may indicate that the kidneys are unable to effectively remove urea from the blood. As such, BUN tests can also be used to track the progress of a kidney disease.

What is Creatinine?

Creatinine is a waste product that forms when creatine (a supplier of energy to the muscles) breaks down. Creatinine levels are often assessed to determine how well the kidneys are working or before and after dialysis to monitor effectiveness of treatment. Frequently, healthcare providers will use your blood creatinine level, along with your age, race, sex, and other factors to calculate your glomerular filtration rate (GFR). The GFR is considered to be the best measure of kidney function. Our kidneys are full of small blood-filtering structures called nephrons. The nephrons remove waste products, excess water, and other impurities from the blood. The toxins are then stored in the bladder and removed in urine. Creatinine is one of the substances that our kidneys normally remove from the body. An abnormally high level of creatinine in the blood may indicate that the kidneys are damaged or impaired. Creatinine tests are often run along with several other tests, including a blood urea nitrogen test, a basic metabolic panel, or a comprehensive metabolic panel to evaluate major organ systems.

What is the BUN to Creatinine ratio?

A BUN/Creatinine ratio is found by dividing the BUN count with the creatinine count.

Occasionally, a health practitioner will look at the ratio between a person’s BUN and blood creatinine to help determine what is causing these concentrations to be higher than normal.

Why is it useful?

The BUN/Creatinine ratio is useful in the differential diagnosis of acute or chronic renal disease.

Normal levels:

Because the body produces much more BUN than creatinine, the ideal BUN/Creatinine ratio lies somewhere between 10:1 and 20:1.

An increased ratio:

An increased ratio may be due to a condition that causes a decrease in the flow of blood to the kidneys, such as congestive heart failure or dehydration. It may also be seen with increased protein, from gastrointestinal bleeding, or increased protein in the diet.

A decreased ratio:

The ratio may be decreased with liver disease (due to decrease in the formation of urea) and malnutrition.

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