CPT code 84520: Blood urea nitrogen, quantitative assay2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Quantitative blood urea nitrogen testing measures circulating urea nitrogen and is reported when clinicians assess kidney function or monitor renal status.
Medicare pays $3.95 for 84520 under the 2026 Clinical Laboratory Fee Schedule: one national amount, the same in every state and setting.
Medicare lab fee · CLFS 2026 Q4
National CLFS amount
$3.95
In effect since Jan 1, 2026. The same amount in every state, payment locality and setting.
- Geographic adjustment
- None
- Office vs facility
- Same
- Since 2020
- Unchanged
- QW · CLIA-waived test
- $3.95
Medicare pays the lesser of the lab’s charge and this amount. Patients usually owe no Part B deductible or coinsurance for covered clinical lab tests.
On this page 8 sections
What 84520 covers
This assay measures urea nitrogen in blood quantitatively. Clinicians commonly order it to assess kidney function, follow renal impairment, or evaluate changes in hydration or metabolic status. Hospital and independent laboratories perform the assay; eligible waived testing sites may perform the CLIA-waived version. It is often considered alongside serum creatinine or as part of a chemistry panel when a broader evaluation is ordered.
Report 84520 for quantitative blood urea nitrogen testing, rather than a semi-quantitative assay or a urine urea nitrogen test. When the complete basic metabolic panel is performed, report the panel code rather than separately coding its included BUN component. The CLIA-waived version is identified with modifier QW and is available to sites holding a CLIA certificate of waiver. Medicare pays through the CLFS only: the 2026 national amount is $3.95, unchanged since 2020. The amount applies in every locality, with no geographic or office/facility adjustment.
This summary was written with AI assistance from CMS Clinical Laboratory Fee Schedule data. Amounts on this page come directly from CMS files.
How Medicare pays 84520
Clinical lab tests aren’t priced like physician services. They’re paid from their own fee schedule, with its own rules. See the whole lab fee schedule.
One national amount
CMS sets a single Clinical Laboratory Fee Schedule amount for 84520. There’s no geographic (GPCI) adjustment, so it pays the same in every state and payment locality.
No office or facility rate
Lab tests aren’t built from relative value units, so there’s no office and facility split: the place of service doesn’t change the CLFS amount.
Updated every quarter
CMS republishes the CLFS each quarter. New tests, often proprietary laboratory analyses (PLA codes), join during the year; existing amounts are updated each January.
Excluded from the physician fee schedule
The physician fee schedule lists 84520 with status X (excluded by statute), so the test itself is paid only from the CLFS.
CLIA-waived version (QW)
CMS also lists 84520 with modifier QW, the version labs holding a CLIA certificate of waiver bill. It pays $3.95.
84520 on the lab fee schedule since 2020
84520 · CLFS 2026 Q4 (current)
$3.95
Unchanged since Jan 1, 2020
27 quarterly CLFS releases on file, first CLFS 2020 Q1. A code missing from a quarter wasn’t on that release.
84520 compared with similar tests
- 84525Urea nitrogenSemiquantitative$5.13
- Choose 84520 for quantitative blood urea nitrogen testing; 84525 is the semi-quantitative test.
- 84540Urine urea nitrogenUrine specimen$5.56
- 84540 measures urine urea nitrogen. Use 84520 for the quantitative blood assay.
- 84545Urea clearanceClearance calculation$7.20
- 84545 is for urea nitrogen clearance testing, not the standalone quantitative blood urea nitrogen assay.
- 80048Basic metabolic panelTotal calcium$8.46
- 80048 represents a complete basic metabolic panel that includes BUN. Use it when the full panel is performed rather than separately reporting the included BUN test.
84520 billing questions
When should 84520 be used instead of 84525?
Use 84520 for a quantitative blood urea nitrogen result. Code 84525 describes a semi-quantitative urea nitrogen test.
Is 84520 used for urine urea nitrogen?
No. Code 84520 is for quantitative blood testing; 84540 is the urine urea nitrogen assay.
Can 84520 be reported separately with a basic metabolic panel?
The basic metabolic panel includes a BUN component. When the complete panel is performed, report the panel rather than separately reporting 84520 for that included component.
When is modifier QW appropriate?
Use QW for the CLIA-waived version when performed by a site holding a CLIA certificate of waiver.
How many units should be reported?
Report one unit for one completed quantitative assay. The numeric concentration in the result does not create additional units.
How does Medicare pay for 84520?
Medicare pays the test through the CLFS. The same national amount applies across localities, without an office or facility adjustment.
Where this amount comes from
FeeBase reads lab amounts directly from the CMS Clinical Laboratory Fee Schedule file for the quarter: one row per code, with its payment indicator and national amount. Contractor-priced tests are labeled, never given a made-up amount. Amounts are Medicare payment limits, not a patient’s bill or a commercial rate.
CMS CLFS 2026 Q4 · effective Oct 1, 2026 through the day before Jan 1, 2027
Show the CMS file line behind this amount
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