CPT code 80203: Zonisamide level, quantitative drug assay2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Quantitative zonisamide testing measures an antiseizure medication level, commonly to assess seizure control, possible toxicity, adherence, or medication management.
Medicare pays $13.25 for 80203 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 80203 covers
80203 identifies a quantitative assay of zonisamide, an antiseizure medicine used to treat seizure disorders. Clinicians may order a zonisamide concentration when assessing seizure control, possible medication toxicity, adherence, or medication management after a dose change. A clinical laboratory performs the assay; neurologists and other clinicians treating patients with seizure disorders may order it.
Report 80203 for zonisamide rather than another medication-specific assay or a general quantitative drug assay. Medicare pays the test under the CLFS at one nationally set amount per code; the 2026 national amount is $13.25, unchanged from 2020. The amount applies across states and localities, without geographic or office-versus-facility adjustment. Medicare pays this test only through the CLFS, not the physician fee schedule.
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 80203
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 80203. 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 80203 with status X (excluded by statute), so the test itself is paid only from the CLFS.
80203 on the lab fee schedule since 2020
80203 · 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.
80203 compared with similar tests
- 80201Topiramate levelTopiramate-specific assay$11.92
- 80201 identifies a topiramate assay. Use 80203 when the measured drug is zonisamide.
- 80235Lacosamide assayDrug measurement$27.11
- 80235 identifies a lacosamide assay. Use 80203 when the measured drug is zonisamide.
- 80299Drug assayUnlisted therapeutic drug$18.64
- 80299 is a general quantitative drug assay code for situations where a more specific assay code does not fit. Use 80203 for zonisamide.
80203 billing questions
When might a clinician order a zonisamide level?
It may be ordered when assessing seizure control, possible medication toxicity, adherence, or medication management after a dose change.
Should 80203 be used for a topiramate level?
No. 80203 is specific to zonisamide; 80201 identifies a topiramate assay.
How does Medicare pay for 80203?
Medicare pays it under the CLFS at one national amount per code, with no geographic or office-versus-facility adjustment. The test is paid only through the CLFS.
When would 80299 be considered instead?
80299 is for a quantitative drug assay when a more specific assay code does not fit. Use 80203 for a zonisamide assay.
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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