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Understanding High Urea Nitrogen: Causes, Symptoms And Treatments

September 21, 2019

Describing the human body as complex is definitely an understatement. It’s designed with intricate systems that work together to accomplish elaborate bodily functions and chemical reactions. Granted, each of these processes involves numerous enzymes and substances. An example is urea nitrogen, a product of protein synthesis. This article will be focusing on the implications of a high urea nitrogen level, as well as its causes, symptoms, and treatment options.


Urea Nitrogen

A reputed medical website run by the U.S. National Library of Medicine defines urea nitrogen as one of the many waste products that the kidneys filter from the blood. The Mayo Clinic describes this process in detail. Firstly, ammonia—which has nitrogen—is produced in the liver after synthesizing the proteins utilized by the cells. The nitrogen then combines with various elements including hydrogen, oxygen, and carbon, leading to the formation of urea. After it is formed, the urea is transported through blood circulation from the liver to the kidneys, where it will be filtered from the blood and expelled through the urine.

According to an article reviewed by registered nurse Carissa Stephens, because the kidneys are the organs that serve as the body’s filters, their main function is to expel waste and potentially harmful substances. However, when the kidneys are unhealthy or damaged, they fail to remove some waste products, consequently enabling them to go back to the bloodstream. This typically explains why the level of blood urea nitrogen becomes higher than the normal range.

Urea Nitrogen Level

The best method to determine your urea nitrogen levels is by undergoing a blood urea nitrogen (BUN) test. A BUN test is requested by a physician to determine how well your kidneys are functioning. If your kidneys are unhealthy, they will not be able to remove urea from the blood, thus causing a rise in your BUN level. Other reasons behind a high urea nitrogen level are dehydration, heart failure, or regular consumption of huge quantities of protein.

Your BUN test may also be lower than the normal range. In this case, it may signal liver disease. Other causes are overhydration from excessive fluid intake, inadequate dietary protein, and malnutrition. However, it’s important to note that an abnormal BUN level does not always indicate health conditions, considering that an otherwise healthy pregnant woman can have a low BUN level in her second or third trimester.

The Mayo Clinic reports that BUN test results are given in milligrams per deciliter (mg/dL) in the United States. Internationally, the results are measured in millimoles per liter (mmol/L). The normal ranges depend on factors such as the patient’s age and the reference range used by the laboratory clinic. However, in general, the normal range for adults is around 7 to 20 mg/dL or 2.5 to 7.1 mmol/L.

It’s important to consider that aging may cause blood urea nitrogen levels to rise. Infants under 12 months old have lower levels than people in most age groups. Children have varying levels of urea nitrogen depending on the reference range, but according to the University of Michigan, their normal range is between 5 to 18 mg/dL.



As stated above, an abnormal amount of urea nitrogen does not always indicate health complications. Some causes of a high BUN level that are not harmful include having a protein-rich diet or taking certain drugs such as antibiotics.

However, an increased level can also mean health problems. Primarily, it’s associated with kidney damage or disease that may be caused by high blood pressure or diabetes—two main conditions that affect the kidneys. A severe condition that is also characterized by high BUN levels is uremia, a side effect of kidney failure. Individuals suffering from this condition have urea, proteins, creatinine, and other components of urine in their blood. Because the blood travels to almost every system, this contamination is considered by health professionals as a medical emergency.

A higher than normal level of BUN may also signal tissue damage from severe burns, Addison’s disease, urinary tract obstruction, congestive heart failure, dehydration, shock, and low blood flow to the kidneys. When the BUN level’s comparison to creatinine amounts is significantly high, the likely cause is internal bleeding either in the respiratory tract or gastrointestinal tract.


According to MedlinePlus of the U.S. National Library of Medicine, your healthcare provider may require you to have your BUN levels checked if you are suspected of having kidney disease. If that is the case, you may notice symptoms such as persistent urges to urinate, painful urination, recurring fatigue, water retention in the legs, feet or arms, muscle cramps, and insomnia.

Symptoms however vary based on the condition causing your abnormal urea nitrogen level. For instance, if the cause is gastrointestinal bleeding, the National Institute of Diabetes and Digestive and Kidney Diseases Health Information Center states that you may experience symptoms which include black stool, blood in the stool or vomit, dark-colored vomit, fatigue, shortness of breath, abdominal cramps, dizziness, paleness, rapid pulse, little urination, and low blood pressure.

If the cause of your high BUN results is uremia, the symptoms are electrical sensations in the or numbness in the hands and feet, exhaustion, confusion, nausea, poor appetite, weight loss, acid reflux, high blood pressure, swelling in the ankles or feet, skin itching and dryness, and frequent urination.



Considering that there are different potential causes of a high BUN level, the treatment options widely vary. The priority is to manage your specific condition and the normalizing of your BUN level may follow. For example, if the cause is uremia, the treatment requires being admitted in a hospital and receiving elaborate medications. If the cause is Addison’s disease, hormone replacement therapy may be needed to manage the condition. Simply put, the treatment is significantly relative.

However, if the cause is not a severe complication, a higher than normal BUN level can be easily addressed without having to undergo medical treatment. For example, if the cause is dehydration, all you have to do is drink more liquids. It’s also advisable to discuss your recommended daily fluid intake with your healthcare provider. Another example is if the cause is a diet high in protein. Reducing your consumption of protein-rich food will yield results of a normal BUN level.

To sum up, the first step in determining the appropriate treatment is identifying the reason behind your abnormal urea nitrogen level. It’s suggested that you coordinate closely with a doctor to ensure that you receive the most suitable treatment for your condition.