CPT code 80165: Valproic acid, free level2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures free valproic acid concentration for therapeutic drug monitoring when clinicians need the unbound level rather than a total concentration.
Medicare pays $13.54 for 80165 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 80165 covers
Code 80165 identifies laboratory measurement of free, or unbound, valproic acid, also called valproate. The result quantifies the fraction not bound to circulating proteins, unlike a total valproic acid result. Clinicians may use free concentrations in therapeutic drug monitoring when assessing valproate exposure, including when a total concentration may not fully represent the free drug level. Clinical laboratories perform the assay and report the concentration for the treating clinician.
Report 80165 for a free valproic acid measurement; use 80164 when the assay measures total valproic acid. Medicare pays the test only through the CLFS. The 2026 national CLFS amount is $13.54, unchanged from 2020 through 2026; the same amount applies 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 80165
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 80165. 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 80165 with status X (excluded by statute), so the test itself is paid only from the CLFS.
80165 on the lab fee schedule since 2020
80165 · 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.
80165 compared with similar tests
- 80164Valproate levelTotal concentration$13.54
- 80164 measures total valproic acid; 80165 measures only the unbound fraction. Select the code that matches the assay performed.
- 80157Carbamazepine levelUnbound carbamazepine$13.25
- 80157 is for free carbamazepine, not valproic acid. The drug measured determines the code.
- 80163Digoxin assayFree concentration$13.28
- 80163 measures free digoxin. Use 80165 only when the free analyte is valproic acid.
80165 billing questions
When should 80165 be reported instead of 80164?
Report 80165 when the laboratory measures free valproic acid. Report 80164 when it measures total valproic acid.
Can the free and total valproic acid assays be reported together?
They can be reported when both measurements are performed and documented. Use 80165 for the free measurement and 80164 for the total measurement.
Does 80165 include physician interpretation?
Medicare pays 80165 through the CLFS only; it does not have a separate physician interpretation payment under this code.
How is 80165 paid under Medicare?
Medicare pays one national CLFS amount across states and localities, with no office or facility payment difference.
Is 80165 the right code for free carbamazepine?
No. 80165 is for free valproic acid; 80157 is for free carbamazepine.
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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