CPT code 80157: Carbamazepine level, unbound carbamazepine2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures the unbound fraction of carbamazepine for therapeutic drug monitoring when a free concentration is needed alongside or instead of a total level.
Medicare pays $13.25 for 80157 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
$13.25
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 80157 covers
This assay measures carbamazepine that is not bound to proteins, rather than the combined free and protein-bound concentration measured by a total-level assay. Clinicians may use the free concentration in therapeutic drug monitoring when a total level may not fully reflect the drug’s available concentration. Carbamazepine is commonly monitored in patients treated for seizure disorders. Clinical laboratories perform the assay and report the result to the ordering clinician.
Report 80157 when the assay performed measures free carbamazepine; 80156 represents the total-drug assay. Report one unit for each free carbamazepine assay performed. Medicare pays 80157 through the CLFS only. The 2026 national CLFS amount is $13.25, unchanged since 2020. The amount is the same across states and localities, with no office or facility payment difference.
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 80157
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 80157. 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 80157 with status X (excluded by statute), so the test itself is paid only from the CLFS.
80157 on the lab fee schedule since 2020
80157 · CLFS 2026 Q4 (current)
$13.25
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.
80157 compared with similar tests
- 80156Carbamazepine levelTotal concentration$14.57
- 80156 measures total carbamazepine; 80157 measures only the unbound fraction. Select the code that matches the assay performed.
- 80161Carbamazepine metabolite10,11-epoxide$18.64
- 80161 measures carbamazepine-10,11-epoxide, a metabolite, rather than free carbamazepine. The assays measure different analytes.
- 80165Valproic acidFree level$13.54
- 80165 measures free valproic acid, not carbamazepine. Choose it when the medication being monitored is valproic acid.
80157 billing questions
When should 80157 be reported instead of 80156?
Report 80157 when the assay measures unbound carbamazepine. Use 80156 for a total carbamazepine concentration; the two assays measure different quantities.
What does the free carbamazepine result show?
It measures carbamazepine that is not bound to proteins, rather than the combined free and protein-bound concentration measured by a total-level assay.
Can 80157 be reported with the carbamazepine metabolite assay?
80161 measures carbamazepine-10,11-epoxide, a distinct metabolite. It may be ordered alongside 80157 when the clinician is evaluating both the parent drug and its metabolite.
How many units should be reported?
Report one unit for each free carbamazepine assay performed. A separate total carbamazepine assay is reported with 80156.
How does Medicare pay for 80157?
Medicare pays this test through the CLFS only. The national amount is uniform across localities and does not vary between office and facility 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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