CPT code 80178: Lithium level, quantitative drug monitoring2026 Medicare lab fee · Clinical Laboratory Fee Schedule
A lithium assay measures the drug concentration to monitor therapy, support dose adjustment, or assess possible toxicity.
Medicare pays $6.61 for 80178 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
$6.61
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
- QW · CLIA-waived test
- $6.61
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 80178 covers
This laboratory assay measures lithium concentration in blood, commonly using a serum specimen. It is ordered to monitor patients receiving lithium, including people treated for bipolar disorder, and to help assess possible toxicity or guide treatment changes. The test may be performed by a clinical laboratory or, for the CLIA-waived version, by a site holding a CLIA certificate of waiver. Ordering clinicians commonly include psychiatrists, primary care providers, and clinicians evaluating a patient for suspected toxicity.
Report one service for the lithium assay performed; do not substitute another medication-level code based on the patient's treatment. When the waived version is performed under the applicable waived conditions, report modifier QW. Medicare pays this test only under the CLFS. The 2026 national CLFS amount is $6.61, unchanged since 2020; the same amount applies across states and localities, without an office or facility 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 80178
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 80178. 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 80178 with status X (excluded by statute), so the test itself is paid only from the CLFS.
CLIA-waived version (QW)
CMS also lists 80178 with modifier QW, the version labs holding a CLIA certificate of waiver bill. It pays $6.61.
80178 on the lab fee schedule since 2020
80178 · CLFS 2026 Q4 (current)
$6.61
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.
80178 compared with similar tests
- 80164Valproate levelTotal concentration$13.54
- 80164 measures total valproic acid, not lithium. Select the assay based on the medication being measured.
- 80179Salicylate assaySalicylate measurement$18.64
- 80179 measures salicylate. It is distinct from a lithium level even when medication toxicity is being evaluated.
- 80185Phenytoin levelTotal drug concentration$13.25
- 80185 measures total phenytoin. Use it for phenytoin monitoring rather than lithium monitoring.
80178 billing questions
When should 80178 be reported instead of another drug assay?
Report 80178 when the laboratory measures lithium. Use a different drug assay code when the analyte measured is another medication, such as valproic acid or phenytoin.
Is modifier QW appropriate for every lithium level?
Use QW for the CLIA-waived version when it is performed by a site holding a CLIA certificate of waiver. The modifier identifies the waived test, not every lithium assay.
How many units should be reported?
Report the assay performed for the specimen tested. Do not multiply units based on the number of medications the patient takes.
How does Medicare pay for 80178?
Medicare pays 80178 under the CLFS at one national amount that applies 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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