CPT code 84436: Total T4, total thyroxine2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures total thyroxine in blood to support evaluation or monitoring of thyroid function, distinct from free thyroxine and neonatal thyroxine testing.
Medicare pays $6.87 for 84436 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
$6.87
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 84436 covers
This laboratory assay measures total thyroxine (T4) in a blood sample, including both protein-bound and unbound hormone. Clinicians may order it when evaluating suspected hypothyroidism or hyperthyroidism and when monitoring thyroid disease. It is often interpreted with thyroid-stimulating hormone (TSH) and other thyroid tests. Because total T4 includes the protein-bound portion, it answers a different question from a free T4 assay. Clinical laboratories perform and report the test for patients in outpatient and hospital settings.
Report code 84436 for a total T4 assay performed. Medicare pays it only through the Clinical Laboratory Fee Schedule (CLFS), not the physician fee schedule. The 2026 national CLFS amount is $6.87 and has been unchanged since 2020. The same amount applies in every state and locality, 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 84436
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 84436. 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 84436 with status X (excluded by statute), so the test itself is paid only from the CLFS.
84436 on the lab fee schedule since 2020
84436 · CLFS 2026 Q4 (current)
$6.87
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.
84436 compared with similar tests
- 84439Free T4Unbound thyroxine$9.02
- Code 84436 measures total T4, including its protein-bound portion; code 84439 measures free T4.
- 84437Neonatal T4Elution-based assay$6.47
- Code 84437 identifies neonatal thyroxine testing; use 84436 for the general total T4 assay.
- 84443TSH testThyroid-stimulating hormone$16.80
- Code 84443 measures TSH, a different thyroid-function marker. It may be ordered alongside total T4, but it is not a T4 assay.
- 84479Thyroid uptakeUptake or binding ratio$6.47
- Code 84479 reports a thyroid hormone uptake or binding-ratio test; code 84436 measures total thyroxine directly.
84436 billing questions
When should a laboratory report total T4 rather than free T4?
Report total T4 when the ordered test measures bound and unbound thyroxine together. Use the free T4 code when the requested result is specifically unbound thyroxine.
Is total T4 the same test as neonatal thyroxine?
No. Code 84436 identifies total thyroxine testing; code 84437 identifies the neonatal thyroxine test.
What specimen does the assay use?
Total T4 is measured from a blood sample.
Can total T4 be reported with a TSH test?
Yes. TSH is commonly ordered alongside total T4 in thyroid-function evaluation; report each test performed.
How does Medicare pay for this test?
Medicare pays code 84436 through the CLFS at one national amount, without locality or office-versus-facility variation.
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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