Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Blood urea nitrogen (BUN) is a measure of the amount of nitrogen in the blood that comes from urea, a waste product formed in the liver. It is an important indicator of kidney function and hydration status.
5 Must Know Facts For Your Next Test
BUN levels are used to assess kidney function and can indicate renal disease or dehydration.
Urea is produced in the liver through the metabolism of proteins and is excreted by the kidneys.
Normal BUN levels typically range from 7 to 20 mg/dL for adults.
Elevated BUN levels can be caused by high protein intake, heart failure, gastrointestinal bleeding, or severe dehydration.
Low BUN levels might indicate liver dysfunction or malnutrition.
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Related terms
Urea: Urea is a waste product formed in the liver from ammonia and carbon dioxide during protein metabolism.
Kidney Function: Kidney function refers to how well the kidneys filter blood and produce urine, removing waste products from the body.
Dehydration: Dehydration occurs when there is an excessive loss of body fluids, which can affect various bodily functions including kidney performance.