Category: Blood Test
A Blood Urea Nitrogen (BUN) Test is a blood test used to measure the amount of urea nitrogen present in the blood. Urea is a waste product produced by the liver when the body breaks down proteins. Healthy kidneys filter urea from the blood and remove it through urine. Therefore, measuring BUN levels helps doctors evaluate how effectively the kidneys are removing waste from the body.
The BUN test is an important part of assessing kidney function and overall metabolic health. Increased BUN levels may indicate that the kidneys are not filtering waste properly, which can occur in conditions such as chronic kidney disease, kidney failure, dehydration, urinary blockage, or heart failure. Low BUN levels may sometimes be associated with low protein intake, liver disease, malnutrition, or excessive fluid intake.
Doctors commonly recommend a BUN test for patients experiencing symptoms such as fatigue, swelling in the legs or face, changes in urination, nausea, vomiting, loss of appetite, confusion, or weakness. It is also frequently performed for people with diabetes, high blood pressure, kidney problems, heart disease, or those taking medications that may affect kidney function.
The test requires a small blood sample collected from a vein in the arm. It is often performed together with other kidney tests such as Creatinine Test and eGFR to provide a complete evaluation of kidney health. No major preparation is usually required, although patients should inform their doctor about medications and supplements.
Regular monitoring of BUN levels helps detect kidney problems at an early stage and allows timely treatment. Maintaining proper hydration, controlling blood pressure, managing diabetes, and following medical advice can help protect kidney function and prevent serious complications.
The BUN Test is performed to evaluate kidney function, detect kidney damage, monitor chronic kidney disease, assess dehydration, monitor patients taking kidney-affecting medications, evaluate waste removal by kidneys, and support diagnosis of conditions affecting kidney and liver health.
No special preparation is usually required for a BUN Test. Patients can normally eat and drink before the test unless other fasting tests are being performed at the same time. Inform the doctor about any medications, supplements, high-protein diets, or existing medical conditions that may affect results.
Adults: 7–20 mg/dL
Children: 5–18 mg/dL
Infants: 5–18 mg/dL
(Normal ranges may vary slightly depending on the laboratory.)