CPT code 82140: Ammonia, blood ammonia level2026 Medicare lab fee · Clinical Laboratory Fee Schedule
A blood ammonia assay measures circulating ammonia and is ordered in evaluations of suspected hepatic encephalopathy or metabolic disorders.
Medicare pays $14.57 for 82140 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
$14.57
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 82140 covers
This assay measures ammonia in a blood specimen, commonly plasma. Clinicians may order it when evaluating altered mental status in a patient with significant liver disease or when a urea-cycle or other metabolic disorder is suspected. The result is interpreted alongside the patient’s presentation and other findings; an elevated concentration alone does not establish the cause of symptoms. Ammonia can rise after collection, so prompt processing under the performing laboratory’s specimen-handling protocol matters. Hospital and independent laboratories commonly perform and report the assay for outpatient and inpatient evaluations.
Report 82140 for the ammonia assay performed. Medicare pays it only through the CLFS, at one national amount across localities and with no office or facility payment difference. The 2026 national CLFS amount is $14.57, unchanged since 2020. 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 82140
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 82140. 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 82140 with status X (excluded by statute), so the test itself is paid only from the CLFS.
82140 on the lab fee schedule since 2020
82140 · CLFS 2026 Q4 (current)
$14.57
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.
82140 compared with similar tests
- 80076Liver panelSeven liver chemistry tests$8.17
- 80076 reports a hepatic function panel, not an ammonia assay. Report 82140 separately when ammonia is measured.
- 82139Amino acidsSix or more, quantitative$16.87
- 82139 measures six or more amino acids quantitatively; 82140 measures ammonia. They may be ordered together but represent distinct tests.
82140 billing questions
When is 82140 appropriate?
Use it for a blood ammonia assay, such as during evaluation of suspected hepatic encephalopathy or a possible urea-cycle disorder. It does not represent a liver function panel.
Is ammonia included in a hepatic function panel?
No. A hepatic function panel such as 80076 reports a separate group of liver-related tests; ammonia is a distinct assay.
How many units should be reported?
Report one unit for one ammonia assay. Do not use the number of analytes in a separate panel to determine units for 82140.
How does Medicare pay for 82140?
Medicare pays the assay through the CLFS at one national amount. Payment is the same across localities and does not vary between office and facility settings.
Does 82140 include a physician interpretation?
82140 reports the laboratory assay, which Medicare pays only through the CLFS.
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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