CPT code 80161: Carbamazepine metabolite, 10,11-epoxide2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures carbamazepine’s 10,11-epoxide metabolite for therapeutic drug monitoring, including evaluation of suspected toxicity or an unexpected response during carbamazepine treatment.
Medicare pays $18.64 for 80161 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
$18.64
In effect since Jan 1, 2026. The same amount in every state, payment locality and setting.
- Geographic adjustment
- None
- Office vs facility
- Same
- Since 2021
- 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 80161 covers
This laboratory assay measures carbamazepine-10,11-epoxide, an active metabolite of carbamazepine, an antiseizure medication. A clinician may order it during therapeutic drug monitoring when assessing suspected toxicity, an unexpected response, or whether the metabolite contributes to the patient’s clinical picture. A clinical laboratory measures the analyte in a blood specimen; results are interpreted with the patient’s treatment and other clinical findings. The assay is distinct from testing total or free parent carbamazepine.
Report 80161 for the epoxide measurement when that assay is ordered and performed; it does not represent a total or free carbamazepine result. Medicare pays the test only through the CLFS. The 2026 national CLFS amount is $18.64, unchanged from 2021 through 2026. The same national amount applies across states and localities, with no office-versus-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 80161
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 80161. 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 80161 with status X (excluded by statute), so the test itself is paid only from the CLFS.
80161 on the lab fee schedule since 2021
80161 · CLFS 2026 Q4 (current)
$18.64
Unchanged since Jan 1, 2021
24 quarterly CLFS releases on file, first CLFS 2021 Q1. A code missing from a quarter wasn’t on that release.
80161 compared with similar tests
- 80156Carbamazepine levelTotal concentration$14.57
- 80156 measures total parent carbamazepine; 80161 measures its 10,11-epoxide metabolite. Report the code matching the analyte tested.
- 80157Carbamazepine levelUnbound carbamazepine$13.25
- 80157 measures free parent carbamazepine, not the epoxide metabolite. Use it when the ordered analyte is unbound parent drug.
80161 billing questions
How does 80161 differ from total carbamazepine testing?
80161 measures the 10,11-epoxide metabolite; 80156 measures parent carbamazepine. Choose the assay that matches the analyte ordered.
Can 80161 and 80156 be reported for the same specimen?
Yes, when both assays are ordered and performed. Report each test for its respective analyte.
What should the order or record identify?
It should identify the carbamazepine-10,11-epoxide assay and support the clinical reason for measuring the metabolite.
Does Medicare pay 80161 under the physician fee schedule?
No. Medicare pays 80161 through the CLFS, with one national amount applying across localities and 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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