CPT code 80164: Valproate level, total concentration2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures total valproic acid concentration for therapeutic drug monitoring, including treatment management for epilepsy or bipolar disorder.
Medicare pays $13.54 for 80164 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
$13.54
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 80164 covers
This assay measures total valproic acid, also called valproate, concentration, including bound and unbound drug. Clinicians use therapeutic drug monitoring when treating epilepsy or bipolar disorder, such as when evaluating response or a possible medication-related problem. Clinical laboratories perform and report the assay. The total result differs from a free valproic acid measurement, which reports only the unbound fraction.
Report 80164 when the assay measures total valproic acid; report 80165 for free valproic acid. Medicare pays 80164 only through the CLFS, at one national amount across states and localities, with no geographic or office-versus-facility adjustment. The 2026 national CLFS amount is $13.54, unchanged since 2020. This test is paid 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 80164
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 80164. 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 80164 with status X (excluded by statute), so the test itself is paid only from the CLFS.
80164 on the lab fee schedule since 2020
80164 · CLFS 2026 Q4 (current)
$13.54
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.
80164 compared with similar tests
- 80165Valproic acidFree level$13.54
- 80164 is for total valproic acid; 80165 is for the free fraction. Select the code that matches the assay performed.
- 80156Carbamazepine levelTotal concentration$14.57
- 80156 measures total carbamazepine, not valproic acid. Choose according to the medication measured.
- 80168Ethosuximide level$16.34
- 80168 measures ethosuximide. It is not the code for a valproic acid concentration.
80164 billing questions
When should 80164 be used instead of 80165?
Use 80164 for total valproic acid concentration. Use 80165 when the assay measures the free, or unbound, fraction.
Does 80164 report a total or free drug concentration?
It reports total valproic acid, including bound and unbound drug; it is not the code for the free fraction.
Which code applies to carbamazepine monitoring?
Use 80156 for total carbamazepine and 80157 for free carbamazepine. Code 80164 is for total valproic acid.
How does Medicare pay for 80164?
Medicare pays one national CLFS amount across localities and settings. The test is paid 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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