CPT code 84425: Thiamine test, vitamin B-1 level2026 Medicare lab fee · Clinical Laboratory Fee Schedule
The thiamine assay measures vitamin B-1 and is reported when clinicians evaluate suspected deficiency, including nutritional, malabsorptive, alcohol-related, or neurologic presentations.
Medicare pays $21.23 for 84425 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
$21.23
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 7 sections
What 84425 covers
This laboratory assay measures thiamine (vitamin B-1) for evaluation of suspected deficiency. Clinicians may order it when poor nutritional intake, alcohol use disorder, or malabsorption raises concern for depletion, or when neurologic findings prompt evaluation for thiamine deficiency. It is a targeted nutrient assay rather than a broad vitamin panel. Clinical laboratories perform and report the test.
Report 84425 for the thiamine assay. Medicare pays this test only through the CLFS, which sets one national amount per code across states and localities, without geographic adjustment or an office-versus-facility difference. The 2026 national CLFS amount is $21.23, unchanged from 2020 through 2026. The code is excluded from the physician fee schedule, so Medicare payment for the test comes from the CLFS.
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 84425
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 84425. 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 84425 with status X (excluded by statute), so the test itself is paid only from the CLFS.
84425 on the lab fee schedule since 2020
84425 · CLFS 2026 Q4 (current)
$21.23
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.
84425 compared with similar tests
- 84446Vitamin EAlpha-tocopherol level$14.18
- 84425 measures thiamine (vitamin B-1); 84446 measures vitamin E. Select the code for the nutrient assayed.
- 82607Vitamin B12Level assay$15.08
- 82607 measures vitamin B-12, not thiamine. The codes identify separate nutrient assays.
- 82746Folate testSerum specimen$14.70
- 82746 measures folate. Use 84425 for a thiamine assay rather than a folate assay.
84425 billing questions
When should 84425 be reported instead of vitamin B-12 or folate testing?
Report 84425 when the assay measures thiamine (vitamin B-1). Vitamin B-12 and folate assays measure different nutrients and use different codes.
Does 84425 represent a vitamin panel?
No. It represents a thiamine assay, not a panel of vitamins or nutritional markers.
Is modifier 26 used for 84425?
No. Medicare pays 84425 through the CLFS; the code is excluded from the physician fee schedule.
How does Medicare pay for 84425?
Medicare pays one national CLFS amount per code across localities, with no office-versus-facility payment difference.
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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