Definition
What BUN measures
Blood urea nitrogen measures urea, the waste product the liver makes from protein breakdown and the kidneys excrete. It reflects protein intake, hydration, and kidney clearance together.
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Kidney & electrolytesEssentialCompletemg/dL
BUN
Protein waste shaped by kidneys and hydration
Illustrative sample band · Synthetic
15mg/dL
4.6Sample target 8–20 mg/dL25
Why it matters
How clinicians usually read it
Read with creatinine, it separates stories: a high BUN with normal creatinine often points to dehydration or a high-protein pattern rather than kidney trouble.
When it reads low
A lower value can mean
A lower BUN can follow low protein intake, overhydration, or reduced liver urea production. It is usually a context note rather than a concern.
When it reads high
A higher value can mean
A higher BUN can reflect dehydration, a high-protein diet, certain medications, or reduced kidney clearance. The BUN-to-creatinine relationship helps sort those apart.
Questions for a clinician
Bring the number into a real conversation
01
Does my BUN-to-creatinine pattern suggest hydration or kidneys?
02
Is my protein intake high enough to explain this on its own?
03
Should this be rechecked after a normal day of fluids?
Educational boundary
Educational information only. Displayed ranges are illustrative sample bands, not a diagnosis, treatment plan, or substitute for the contracted laboratory report and a qualified clinician.
See it as a sample result
The sample dashboard shows an illustrative reading, target band, and trend for BUN.