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Blood Urea Nitrogen ( BUN)

About the test
What is this test done for?
Blood urea nitrogen or BUN is a routine blood test that measures the nitrogen levels in the blood, which is derived from the waste product urea, thus called urea nitrogen. It helps in assessing the function of kidneys.
Why is it Done?

This is a routine blood test that checks for the amount of urea nitrogen released in the blood by liver or urea nitrogen remaining in the blood after it has been filtered by kidneys.

It helps in

  • Diagnosing kidney disease
  • Monitor patients who have acute or chronic kidney failure
  • Diagnosing malnutrition
  • Dehydration
When should it be performed?

This test is performed

  • If a patient has symptoms of kidney disease
    • Swelling or puffiness of face, especially around eyes
    • Swelling around ankles
    • Urine becomes foamy or bloody
    • Reduced amount of urine
    • Long standing uncontrolled diabetes or blood pressure
    • Weakness and fatigue
  • If a patient has kidney disease and is on treatment, to monitor the functioning of the kidneys
  • As a routine test if a patient has long standing diabetes, blood pressure, or has had an episode of heart attack
  • In a patient on dialysis, to monitor the effectiveness of dialysis
How is it done
A blood sample will be collected from a vein in your arm. No special preparations like fasting required.

The test result is normal, if levels are 7–20 mg/dL. It means

  • Normal functioning of the kidneys
  • Good response to dialysis

The test results are high, if levels are less than20 mg/dL. It means

  • Acute kidney failure
  • Chronic kidney disease
  • Congestive heart attack
  • Heart attack
  • Severe burns
  • Urinary tract obstruction
  • GI bleeding
  • High protein diet
  • Use of medicines like
    • Allupurinol
    • Aminoglycoside
    • Carbamazepine
    • Cephalosporins
    • Cisplatin
    • Indomethacin
    • Methotraxate
    • Methyldopa
    • Penicillamine
    • Rifampin
    • Tetracyclines
    • Vancomycin

In case a patient has existing kidney disease, BUN levels eventually normalizes or remain constant, which indicate no further worsening of kidney disease or adequate response to therapy.

Low BUN levels are not common and are not a cause of concern, but they may be seen in patients who are malnourished or when they are over hydrated.

Other Tests
  • Creatinine
    • It is a blood test carried out to evaluate the amount of creatinine levels in blood
    • High levels of creatinine indicate kidney disease or failure
  • Uric Acid
    • It is a routine blood test carried out to evaluate the amount of uric acid present in the blood
    • High levels of uric acid along with BUN suggest kidney disease
    • Solitary high uric acid levels suggest hyperuricemia or gout
  • Urea
    • It is a routine blood test carried out to evaluate the amount of urea present in the blood
    • High levels of urea suggest kidney disease
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