BUN
Blood Urea Nitrogen
- Sample
- Blood
- Usual units
- mg/dL
Also known as Blood Urea Nitrogen · Urea Nitrogen
What this test measures
Blood urea nitrogen measures the nitrogen portion of urea circulating in blood. It is usually reported in milligrams per deciliter (mg/dL).
Reading your report
There isn’t one standard range for this test — each lab prints its own. Use the range shown next to your result.
BUN unit converter
Convert BUN units
Labs print this test in mg/dL or mmol/L depending on where the sample was run.
Related guides
- Guide
Why the same blood test has different "normal" ranges at different labs
Reference intervals are built from each lab's own population and equipment, which is why two labs can print different ranges for the same sample.
- Guide
Reference interval, cutoff, and the "optimal" numbers online: three different things
The range beside your result, the target a website quotes, and the threshold that defines a condition are built in different ways and answer different questions.
- Guide
Why the same lab printed a different reference range for you this year
Ranges are not fixed constants. The lab can change method, revise its reference group, or apply a range that depends on your age — none of which is an error.
- Guide
Creatinine, eGFR and urea: one measured, the others worked out from it
A kidney panel prints a waste product, an estimate derived from it, and a second waste product measured separately. Which is which, and why eGFR can move when creatinine doesn't.