CPT code 80188: Primidone level, therapeutic drug assay2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures primidone in a patient sample to help clinicians monitor medication levels during treatment, evaluate possible toxicity, or guide dose adjustment.
Medicare pays $16.59 for 80188 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
$16.59
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 80188 covers
This laboratory assay measures primidone, an antiseizure medication used to treat seizure disorders and essential tremor. Clinicians may order it when assessing a patient’s medication level, evaluating possible toxicity or inadequate response, or adjusting treatment. A serum sample is commonly used. Neurologists and other clinicians managing primidone therapy may order the test, which is performed by a clinical laboratory.
Report 80188 for the primidone assay itself. A phenobarbital level may also be ordered because phenobarbital is a metabolite of primidone; that measurement is reported separately. Medicare pays this test through the CLFS, with one national amount across localities and no office-versus-facility payment difference. The 2026 national CLFS amount is $16.59, unchanged since 2020. The test is paid only from 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 80188
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 80188. 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 80188 with status X (excluded by statute), so the test itself is paid only from the CLFS.
80188 on the lab fee schedule since 2020
80188 · CLFS 2026 Q4 (current)
$16.59
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.
80188 compared with similar tests
- 80184Phenobarbital levelQuantitative drug assay$15.30
- 80188 measures primidone; 80184 measures phenobarbital. The assays may be ordered together, but each represents a different drug level.
- 80175Lamotrigine levelQuantitative drug assay$13.25
- 80175 is the lamotrigine assay. Use 80188 when the measured medication is primidone.
- 80177Levetiracetam levelQuantitative concentration$13.25
- 80177 measures levetiracetam, not primidone. Select the code for the medication actually assayed.
80188 billing questions
When should 80188 be reported instead of 80184?
Report 80188 for a primidone measurement and 80184 for a phenobarbital measurement. Primidone’s metabolism to phenobarbital may lead a clinician to order both assays.
Can primidone and phenobarbital levels be reported together?
Yes, when both assays are performed and ordered, report each under its own code: 80188 for primidone and 80184 for phenobarbital.
What specimen is commonly used for 80188?
Serum is commonly used for primidone level testing.
How many units should be reported?
Report one unit for each primidone assay performed. Do not base units on the measured concentration.
How does Medicare pay for 80188?
Medicare pays 80188 through the CLFS at one national amount, with no locality or office-versus-facility adjustment. Payment is through the CLFS rather than the physician fee schedule.
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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