Overview of Blood Urea Nitrogen (BUN)

Blood urea nitrogen may be requested when you do some tests and it is familiar to the people with kidney disease, since it can reflect kidney function from some points. However, there are still people who do not know as much as they should know.

What is blood urea nitrogen? Liver produces ammonia-which contains nitrogen-after it breaks down proteins used by your body’s cells. The nitrogen combines with other elements, such as carbon, hydrogen and oxygen, to urea, which is a chemical waste product and is not toxic. The urea travels from liver to kidneys through bloodstream. Healthy kidneys filter urea and other waster from the blood into the urine.

What is blood urea nitrogen test? A blood urea nitrogen test measures the amount of nitrogen in your blood that comes from the waste product urea. If your urea nitrogen levels are higher than normal, it probably indicates that your kidneys are not working properly. Or it could point to high protein intake, inadequate fluid intake or poor circulation. If a blood urea nitrogen test shows a lower level, it could indicate liver disease, damage, or malnutrition. But a low BUN would not likely be the first indication of liver disease because the blood urea nitrogen test is not used as a screening test for that disorder.

What do the increased BUN and decreased BUN mean? The value of BUN can be divided into three types. One is normal, the other is higher than normal, namely, increased BUN, the last is lower than normal, that is decreased BUN. The three types have different means. If the BUN is normal, there may be no problem with your organs, but if you want to check the renal function, GFR is recommend even the BUN is normal. Increased BUN is influenced by many factors. Diseased or damaged kidneys cause an elevated BUN, because the kidneys are less able to clear urea from the bloodstream. In conditions in which renal perfusion is decreased, such as hypovolemic shock or congestive heart failure, BUN levels rise. A patient who is severely dehydrated may also have a high BUN due to the lack of fluid volume to excrete waste products. Because urea is an end product of protein metabolism, a diet high in protein, such as high-protein tube feeding, may also cause the BUN to increase. Extensive bleeding into the gastrointestinal tract will also cause an elevated BUN because digested blood is a source of urea. For example, a hemorrhage of one liter of blood into the GI tract may elevate the BUN up to 40mg/ml. Decreased BUN is also caused by many aspects. Because urea is synthesized by the liver, severe liver failure causes a reduction of urea in the blood. Just as dehydration may cause an elevated BUN, overhydration causes a decreased BUN. Some medicines such as chloramphenicol and streptomycin can decrease BUN.

The above content is a brief introduction of BUN, If you still have some questions, you can write email to careforkidney@gmail.com.

• Overview of Blood Urea Nitrogen (BUN)
• Patients with Kidney Disease Should Know More about Physical Check-Up
• Clinical Laboratory