BUN Blood Test High: What Does It Mean?

BUN Blood Test Is High: What Does It Mean?

July 19, 2019

Technological advancement has been integral in improving medical practices. In fact, prior to the 1950s, hospital laboratory technicians have conducted diagnostic tests by hand because automated devices have yet to be invented. Today’s generation is fortunate to benefit from health care of better quality. Many elaborate tests now allow medical professionals to determine the health condition of an individual.


BUN Test

A particular example is the blood urea nitrogen (BUN) test, a blood test for finding out if the kidneys are working well. This article will explain what the normal range of BUN levels is and what high BUN test results are likely to signify.

According to the U.S. National Library of Medicine, urea nitrogen is included in many waste products that are removed from the blood by the kidneys. The Mayo Clinic describes this states that ammonia, a substance containing nitrogen, is produced in the liver after breaking down protein compounds that the cells used. Various elements including hydrogen, oxygen, and carbon combine with nitrogen, thus leading to the formation of urea. Lastly, the urea is transported through blood circulation from the liver to the kidneys, where it will be filtered from the blood and released into the urine.

Medical experts assert that the process above can only be completed successfully if the kidneys are healthy. The kidneys’ main function is to expel waste and potentially harmful substances from the bloodstream. However, when the kidneys damaged, they may fail to remove certain substances, allowing them to contaminate the blood.

The levels of urea nitrogen tend to rise when the kidneys aren’t able to filter them from the blood. To determine if one’s levels are within the normal range, a blood urea nitrogen test can be used.


Normal BUN Range

Usually, A BUN test is requested by the referring physician when a patient is suspected of having kidney problems. According to an American health information website, symptoms associated with kidney damage or disease include painful urination, persistent urges to urinate, fatigue, insomnia, muscle pain, and swelling or water retention in the legs, feet or arms.

Other reasons behind a high urea nitrogen level are dehydration and shock due to inadequate fluid intake, heart failure, or regular consumption of huge quantities of protein. Your BUN test may also be lower than the normal range due to liver damage, overhydration from excessive fluid intake, inadequate dietary protein, or malnutrition. However, it’s good to consider that an abnormal BUN level doesn’t always indicate health problems. For instance, a woman can naturally have a low BUN value in her second or third trimester of pregnancy.

According to the Mayo Clinic, BUN test results are given in milligrams per deciliter (mg/dL) in the United States while in the international community, the results are measured in millimoles per liter (mmol/L). Factors affecting what are deemed to be the normal range for BUN levels include the reference range used by the laboratory clinic and the patient’s age. Generally, the normal range for adults is between 7 to 20 mg/dL or 2.5 to 7.1 mmol/L.

As stated, the age of a patient affects his or her normal range because BUN levels tend to rise with aging. Children have varying levels of urea nitrogen, but the reference range provided by the University of Michigan is around 5 to 18 mg/dL. Infants, on the other hand, have significantly lower BUN levels than people in other age groups.



Prior to a BUN test, you may be instructed by your healthcare provider to avoid eating meat or other protein-rich foods for 24 hours as they tend to spike BUN levels. However, some individuals may be asked to fast for a few hours before the test if they are asked to have other blood tests.

A blood sample will be drawn from a vein in your arm. A test tube or vial will be used to collect the sample, a process that most likely does not take more than five minutes.

There are no serious risks to having a BUN test. You may only feel slight bruising or pain from the spot where your blood is drawn, but it usually gets better within a few hours.


Causes of High BUN Value

An abnormal amount of BUN does not always signal severe complications. Having a protein-rich diet or taking certain drugs such as antibiotics can heighten BUN levels in otherwise healthy individuals.

However, high BUN results are often associated with kidney damage or disease. For instance, a severe condition characterized by high BUN values is uremia. Components of urine such as urea, proteins, and creatinine are detected in the blood of people suffering from this condition. This contamination is considered by medical professionals as a medical emergency that requires immediate treatment as blood circulates all throughout the body.

Other causes of a higher than normal BUN level are tissue damage from severe burns, Addison’s disease, urinary tract obstruction, congestive heart failure, dehydration, and low blood flow to the kidneys. If the BUN to creatinine ratio is significantly high, doctors usually associate it with bleeding in the respiratory tract or digestive tract.



There’s no one-size-fits-all treatment for a high BUN level, especially since it’s linked to multiple potential causes. The first step is managing your specific condition as the normalizing of your BUN level will usually follow if underlying causes are successfully treated.

If the cause of your high test result is not a serious complication, BUN levels can be easily regulated with little medical attention and supervision. For instance, if the cause is a diet high in protein, lessening your consumption of protein-rich food will yield results of a normal BUN level. In addition, if the cause is dehydration, all you have to do is discuss your recommended daily fluid intake with your healthcare provider and adjust your intake based on the suggestion.

Simply put, to select the appropriate treatment, it’s vital to first identify the reason behind your heightened urea nitrogen level. While treatment is ongoing, it’s advisable to attend regular assessments and consultations to allow your healthcare provider to track progress and make adjustments as necessary. This way, you’ll be getting the most suitable treatment option for your specific needs.