CPT code 84165: Protein electrophoresis, serum fractionation and quantitation2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Serum protein electrophoresis separates and quantifies protein fractions, commonly helping evaluate monoclonal proteins in suspected plasma-cell disorders or unexplained serum protein abnormalities.
Medicare pays $10.74 for 84165 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
$10.74
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 84165 covers
Serum protein electrophoresis separates serum proteins into fractions and quantifies those fractions. Clinicians commonly order it when evaluating suspected monoclonal gammopathy, multiple myeloma, or unexplained changes in serum proteins. Hospital and independent laboratories perform the analysis on serum; the resulting pattern and fraction measurements help guide further evaluation, including testing to characterize a suspected monoclonal protein.
Report 84165 for the serum electrophoresis service, not separately for each fraction. The laboratory test is paid under the CLFS: the 2026 national amount is $10.74, unchanged since 2020. Medicare uses the same amount nationwide, without locality or office-versus-facility adjustment. A physician’s separate interpretation may be billed under the physician fee schedule with modifier 26.
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 84165
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 84165. 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 84165 with status X (excluded by statute), so the test itself is paid only from the CLFS.
Physician interpretation (modifier 26)
A physician’s interpretation is billed separately with modifier 26 and paid under the physician fee schedule: $17.70 nationally in the office, before locality adjustment.
84165 on the lab fee schedule since 2020
84165 · CLFS 2026 Q4 (current)
$10.74
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.
84165 compared with similar tests
- 84155Total proteinSerum, plasma, or whole blood$3.67
- 84155 measures serum protein concentration; 84165 separates and quantifies serum protein fractions electrophoretically.
- 84166Protein electrophoresisUrine or CSF$17.83
- Choose 84165 for serum. 84166 is used for protein electrophoresis of urine or cerebrospinal fluid.
- 86334ImmunofixationSerum specimen$22.34
- 86334 reports immunofixation, which helps characterize immunoglobulin proteins; it is distinct from serum protein fractionation and quantitation under 84165.
84165 billing questions
When should 84165 be used instead of 84155?
Use 84165 for electrophoretic separation and quantitation of serum protein fractions. Code 84155 reports a serum protein measurement without that fractionation.
How does 84165 differ from 84166?
84165 is for serum protein electrophoresis. 84166 is the related electrophoresis code for urine or cerebrospinal fluid.
Should each protein fraction be billed as a separate unit?
No. Report the electrophoresis service, not a separate unit for each fraction.
Can a physician bill separately for interpreting the study?
Yes. A separate physician interpretation may be billed with modifier 26 under the physician fee schedule.
How does Medicare pay for the laboratory test?
The test is paid under the CLFS at one national amount, the same across localities and office and facility settings.
How does immunofixation relate to serum protein electrophoresis?
Immunofixation, reported with 86334, can be used to further characterize a suspected monoclonal protein identified during evaluation.
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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