What is BUN?
A blood urea nitrogen test is ordered as a diagnostic tool examining liver and/or kidney function. When the liver and kidneys are working properly, BUN levels should be normal. Overproduction in the liver or under-excretion by the kidneys will cause BUN levels to rise above normal. On the flip side, if the liver is not producing enough BUN, levels will show lower than normal.

Patients with kidney or liver disease will have BUN tests regularly to evaluate organ health and disease progression. The test may also be used to gauge how effective treatment has been. If kidney disease is a possible diagnosis, doctors will order BUN and creatinine testing at the same time.

Normal Value Range

• Negative Pregnancy Adult: 7 to 20 mg/dL or 2.5 to 7.1 mmol/L
• Pregnancy Trimester One: 7 to 12 mg/dL or 2.5 to 4.3 mmol/L
• Pregnancy Trimester Two: 3 to 13 mg/dL or 1.1 to 4.6 mmol/L
• Pregnancy Trimester Three: 3 to 11 mg/dL or 1.1 to 3.9 mmol/L

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