Blood urea nitrogen Blood Urea Nitrogen (BUN)
The same protein waste, counted as just its nitrogen part.
Also printed asBUN · Urea Nitrogen · Urea · Blood Urea · Serum Urea
What it measures
The same waste as blood urea, reported as the nitrogen it contains - about half the urea number.
Identical information to urea; labs report one or the other, and reporting both does not mean two findings.
Why it matters for how long you stay well
It carries the same information as urea, so use whichever your lab reports and follow it consistently across reports rather than mixing the two.
How it shows up in daily life
It moves for exactly the same reasons urea does: water, protein and how well the kidneys are clearing.
High and low readings
When it reads high
Dehydration, a high-protein diet, or slower kidney clearance.
When it reads low
Low protein intake, or a liver making less urea.
What moves it
Daily life
- how much protein you eat
- how much water you drink
- hot weather
Medicines known to shift it
- diuretics (raise it)
- steroids (raise it)
- NSAIDs (can raise it)
Listed so a result can be read in context. It is not advice to start, stop or change any medicine; that decision belongs with your physician.
Read it with
Markers that move this one, or that this one moves. One number read alone can mislead.
- Urea, protein wasteKnown mechanism
Urea is part of its calculation
Blood urea nitrogen is the same waste, counted as only the nitrogen inside it. That is why the number is roughly half, and why the two must never be compared.
Common questions
What does Blood Urea Nitrogen (BUN) measure?
The same waste as blood urea, reported as the nitrogen it contains - about half the urea number. Identical information to urea; labs report one or the other, and reporting both does not mean two findings.
What does a high Blood urea nitrogen result usually mean?
Dehydration, a high-protein diet, or slower kidney clearance.
What does a low Blood urea nitrogen result usually mean?
Low protein intake, or a liver making less urea.
What is the usual reference range for Blood urea nitrogen?
A broad adult reference band is 7–20 mg/dL. Labs differ, so read your result against the band printed on your own report.
Educational only, not a diagnosis. A single number means little without your history and the rest of your panel, so discuss your own results with your physician.
Typical adult reference band
- Adults
- 7–20 mg/dL
Labs differ. The band printed on your own report is the one that applies to your result.
Reported in mg/dL
Ageing relevance
3/5
A moderate ageing association; used in clinical longevity panels.
Worth knowing
It is the same waste as urea, reported as only the nitrogen inside it, which is roughly half the number.
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