CPT code 84681: C-peptide, endogenous insulin marker2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures blood C-peptide to assess endogenous insulin production, including during evaluation of diabetes type or unexplained hypoglycemia.
Medicare pays $20.81 for 84681 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
$20.81
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 84681 covers
The assay measures C-peptide in a blood specimen. C-peptide is released when the pancreas processes proinsulin to insulin, so the result can help assess the body's own insulin production. Endocrinologists and clinicians managing diabetes may order the test when evaluating diabetes type or unexplained hypoglycemia. A blood glucose result can provide context for interpreting C-peptide levels.
Report 84681 for the C-peptide assay. Medicare pays the test only through the CLFS, at one national amount that applies across localities and in office and facility settings, without geographic adjustment. The 2026 national CLFS amount is $20.81, unchanged from 2020 through 2025. The code is excluded from the physician fee schedule, so payment is through the CLFS.
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 84681
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 84681. 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 84681 with status X (excluded by statute), so the test itself is paid only from the CLFS.
84681 on the lab fee schedule since 2020
84681 · CLFS 2026 Q4 (current)
$20.81
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.
84681 compared with similar tests
- 83525Insulin assayTotal insulin$11.43
- 83525 measures insulin; 84681 measures C-peptide, which reflects the body's own insulin production.
- 82947Blood glucoseQuantitative, not reagent strip$3.93
- 82947 measures blood glucose concentration. It may accompany C-peptide testing but does not measure insulin production.
- 83036A1c testLaboratory assay$9.71
- 83036 measures hemoglobin A1c for longer-term glycemic assessment; 84681 measures C-peptide to assess endogenous insulin production.
84681 billing questions
When should 84681 be reported instead of an insulin assay?
Report 84681 when the laboratory measures C-peptide. An insulin assay measures insulin itself; the tests may provide complementary information about insulin production.
Can a glucose test be ordered with C-peptide?
Yes. A glucose measurement may be ordered alongside C-peptide to provide context for interpreting endogenous insulin production.
Does 84681 include a separately payable physician interpretation?
Medicare pays 84681 through the CLFS, and the code is excluded from the physician fee schedule.
How does Medicare set payment for 84681?
Medicare uses one national CLFS amount across localities, without geographic or office-versus-facility adjustment.
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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