Urea Nitrogen (BUN) Test
The BUN test measures urea nitrogen, the main waste product from the breakdown of protein in the body, in a blood serum sample. Clinicians use it as one input when evaluating kidney and metabolic function, read alongside other results rather than on its own.
About this test
Urea nitrogen, commonly abbreviated BUN, is the principal waste product left over when the body breaks down protein. The liver produces urea, which then travels through the bloodstream to the kidneys, so its concentration is commonly evaluated as part of assessing kidney and metabolic health.
Because BUN reflects both how much protein is being broken down and how well the kidneys are clearing waste from the blood, a single result does not point to one cause on its own. A clinician reads it in the context of other kidney markers, hydration status, and a person's overall health picture.
Test details
| Quest code | 294 |
|---|---|
| Methodology | Spectrophotometry |
| Sample type | 1 mL serum |
| Collection | Quest patient service center |
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Quest resources
Additional details
What this test looks at
The test reports the concentration of urea nitrogen in a blood serum sample. It is also known as Blood Urea Nitrogen or BUN, names that refer to the same measurement. A rise in this value can reflect several different processes, including increased protein breakdown, reduced blood flow to the kidneys, various kidney conditions, or a blockage in the urinary tract, so it is one piece of information among several a clinician weighs together.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does the BUN test measure?
It measures urea nitrogen, the main waste product left over from the breakdown of protein in the body, in a blood serum sample.
How is the BUN sample collected?
The test uses a 1 mL serum sample from a routine blood draw at a Quest Diagnostics patient service center.
Do I need to prepare for a BUN test?
No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides.
Why is BUN commonly evaluated?
It is commonly evaluated as part of assessing kidney and metabolic health, since urea nitrogen is the principal waste product of protein breakdown that the kidneys clear from the blood.
Can a BUN result tell me what is causing a change in kidney function?
No. It reports one value that can be affected by several different things, including protein breakdown, blood flow to the kidneys, and kidney or urinary tract conditions. A clinician reads it alongside other results and a person's history.
Can I get the Urea Nitrogen test without a doctor's visit or insurance?
Yes. The $15 cash price includes an independent physician's order, so no referral is needed, and insurance is never involved.