Summary & Overview
CPT 84481: Free T3 Laboratory Test
CPT code 84481 designates a laboratory assay for measuring free triiodothyronine (free T3) in patient blood. Free T3 testing is clinically significant for evaluating thyroid function, particularly when TSH and free T4 results are inconclusive or when assessing symptoms of hyperthyroidism or central thyroid disorders. Nationally, this code is relevant across outpatient and inpatient laboratory settings as part of endocrine diagnostic workups.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise review of clinical context for ordering free T3, common sites of service, and expected service line classification. The publication outlines where 84481 fits within laboratory testing workflows and what to expect in payer coverage discussions.
This resource provides benchmarks and coding context, highlights policy updates affecting laboratory billing and Medicare laboratory coverage considerations, and summarizes clinical indications that commonly prompt a free T3 measurement. Data not available in the input for specific associated taxonomies, ICD-10 diagnoses, related codes, and detailed payer-specific reimbursement rates.
Billing Code Overview
CPT code 84481 describes a laboratory assay that measures free triiodothyronine (free T3) concentration in patient blood. This test evaluates the unbound, biologically active fraction of the thyroid hormone T3, used in assessing thyroid function and guiding endocrine management.
Service type: Laboratory diagnostic test
Typical site of service: Clinical laboratory or hospital laboratory
Clinical & Coding Specifications
Clinical Context
A 45-year-old female presents to an outpatient endocrinology clinic with symptoms of palpitations, unexplained weight loss, heat intolerance, and tremor. The clinician suspects thyrotoxicosis and orders a thyroid panel including a serum free T3 level. Blood is drawn in the clinic phlebotomy area and sent to the laboratory. The lab analyst performs 84481 (free T3) using an immunoassay or mass spectrometry platform. Results are reported to the ordering endocrinologist and primary care provider through the electronic health record. The free T3 result is used alongside TSH and free T4 to distinguish hyperthyroidism, assess severity, and guide treatment decisions such as antithyroid medication initiation or dose adjustment. Typical sites of service include outpatient clinic, hospital inpatient laboratory, and independent clinical laboratory.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | When billing separately for the professional interpretation component of the test (rare for routine lab analytes). |
TC | Technical component |