CPT code 83921: Organic acid, single analyte, quantitative2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Reports quantitative measurement of one organic acid, such as methylmalonic acid, when a clinician needs a result for a specific analyte.
Medicare pays $21.21 for 83921 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
$21.21
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
- CMS updates
- Quarterly
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 83921 covers
This laboratory service quantifies one selected organic acid rather than measuring total organic acids or qualitatively identifying multiple acids. Methylmalonic acid is a common example; quantitative testing may support evaluation of vitamin B12 deficiency or methylmalonic acidemia. Clinical laboratories perform and report the assay for a clinician's diagnostic question.
Report 83921 for quantitative measurement of one organic acid. Use 83918 for total organic-acid quantification and 83919 for qualitative organic-acid testing reported for each acid. Medicare pays the test only through the CLFS. The code has one national CLFS amount across localities, with no geographic or office-versus-facility adjustment; the 2026 amount is $21.21, unchanged from 2020 through 2025. The test is excluded from the physician fee schedule by statute.
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 83921
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 83921. 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 83921 with status X (excluded by statute), so the test itself is paid only from the CLFS.
83921 on the lab fee schedule since 2020
83921 · CLFS 2026 Q4 (current)
$21.21
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.
83921 compared with similar tests
- 83918Organic acidsTotal quantitative$23.60
- 83921 represents quantitative testing of one organic acid; 83918 represents quantitative testing of total organic acids.
- 83919Organic acidsQualitative, each specimen$16.45
- 83921 is quantitative testing of one acid. 83919 is qualitative testing, reported for each organic acid.
- 83945Oxalate testOxalate-specific assay$14.45
- 83945 identifies an oxalate assay specifically. Use 83921 for quantitative measurement of a different single organic acid.
83921 billing questions
When should this code be used instead of 83918?
Use this code for quantitative measurement of one selected organic acid. Code 83918 describes quantitative measurement of total organic acids.
How does this code differ from 83919?
This code is for quantitative measurement of one acid. Code 83919 is for qualitative organic-acid testing reported for each acid.
How many organic acids does 83921 represent?
It represents quantitative measurement of one selected organic acid, not a total-organic-acid measurement.
What should the record identify?
It should identify the organic acid measured and that the reported result is quantitative.
Does Medicare pay this test under the physician fee schedule?
No. Medicare pays this test through the CLFS, using one national amount across localities and settings.
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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