Blood Urea Nitrogen

Blood Urea Nitrogen (BUN) is a test that measures the amount of urea nitrogen found in the blood. This test is used to determine how well your kidneys are working. Urea nitrogen is a waste product, produced in the liver due to breakdown of proteins. Normally kidneys filter it and is excrete in the urine. If the level of BUN are high in blood it may be a sign of a kidney or a liver problems. The test is performed if there is a suspect of kidney disease with symptoms of urinary changes, swelling in arms or legs, muscle cramps, or frequent episodes of fatigue. The test may also be done if the doctor suspects kidney damage, to evaluate kidney function, to determine the effectiveness of dialysis or to help in diagnosis of other conditions like liver damage, urinary tract obstruction, congestive heart failure or gastrointestinal bleeding.

Frequently asked questions

How is the blood sample taken?

To take the blood sample, a tourniquet (elastic) band is placed tightly on the upper arm. The patient is then asked to make a fist. This helps in the build-up of blood filling the veins and it becomes easy to collect the blood. The skin is cleaned before inserting the needle in the vein in order to prevent bacteria from entering. Needle is inserted into the vein of the arm and the blood sample is collected in the vacutainer.

In what other conditions is BUN performed?

Doctor may suggest BUN test if you have risk factors for kidney disease like family history of kidney disease, diabetes, hypertension (high blood pressure) and/or heart disease.

What are the signs and symptoms of kidney disease?

The signs and symptoms of kidney disease include: Fatigue, frequent or no urination, urine discolouration (bloody, foamy, dark coloured), swelling of extremities (arms, legs), eyes, face, high blood pressure, nausea, vomiting, etc.

What drugs cause elevated BUN levels?

Elevated BUN levels may be caused by some of the drugs like amphotericin B , carbamazepine , cephalosporin, furosemide , methotrexate, methyldopa, rifampin, spironolactone, tetracycline, thiazide diuretics, vancomycin, etc.,. Not everyone will experience elevated BUN levels with the above mentioned medication. Tell your doctor if you?re taking any of these medications