Blood urea nitrogen (BUN)

Definition

Blood urea nitrogen (BUN) is a measure of the amount of urea nitrogen in the blood, a waste product formed in the liver from protein metabolism. Elevated BUN levels can indicate impaired kidney function or fluid imbalance.

5 Must Know Facts For Your Next Test

1. BUN levels are commonly used to assess renal function and hydration status.
2. Normal BUN levels typically range from 7 to 20 mg/dL.
3. Elevated BUN levels can be caused by kidney dysfunction, dehydration, or high protein intake.
4. Diuretic drugs may affect BUN levels by altering fluid and electrolyte balance.
5. A high BUN-to-creatinine ratio might suggest prerenal causes such as heart failure or dehydration.

Review Questions

• What does an elevated BUN level indicate about kidney function?
• How can diuretic drugs influence BUN levels?
• What is considered a normal range for blood urea nitrogen?

Related terms

Creatinine:

A waste product from muscle metabolism measured alongside BUN to assess kidney function.

Glomerular Filtration Rate (GFR):

An estimate of how much blood is filtered by the glomeruli each minute, used to evaluate kidney performance.

Diuretics:

Medications that promote urine production to help manage fluid volume excess and hypertension.