Overview
CPT® code 84481 is used to report a laboratory test that measures the concentration of free triiodothyronine (T3) in the patient’s serum. Free T3 represents the biologically active, unbound portion of the T3 hormone circulating in the bloodstream. Unlike total T3 tests, which measure both bound and unbound hormone, the free T3 test focuses on the fraction that directly affects cellular metabolism and energy regulation.
When to Use CPT 84481
Report 84481 when evaluating thyroid function, particularly when assessing conditions such as hyperthyroidism, thyrotoxicosis, or when T3 levels appear discordant with TSH or free T4 results. It is also used for monitoring treatment effectiveness in patients with known thyroid disorders or suspected abnormalities in thyroid hormone binding.
Key Requirements
- A serum specimen is required for testing.
- Often ordered alongside TSH (84443) and Free T4 (84439) for a complete thyroid panel.
- The test should be performed when free T3 levels are clinically relevant to the diagnosis or management of thyroid dysfunction.
Billing Guidelines
- Use 84481 for the free T3 measurement only.
- Do not report this code with 84480 (Triiodothyronine, total) for the same specimen.
- If multiple thyroid studies are ordered (TSH, free T4, free T3), each test should be billed separately with its respective CPT code.
- Documentation should include the medical necessity for ordering the test—such as signs of hyperthyroidism, unexplained weight changes, or abnormal TSH levels.
Example Clinical Scenarios
- A patient presents with symptoms of hyperthyroidism but normal T4 levels—ordering a free T3 test helps identify T3 toxicosis.
- A provider monitors thyroid hormone replacement therapy to ensure adequate but not excessive dosing.
Summary
CPT® code 84481 identifies laboratory analysis of free triiodothyronine (T3), a crucial component of thyroid function assessment. Measuring the free form of T3 provides valuable insight into a patient’s metabolic state and helps clinicians fine-tune diagnoses and treatment plans for thyroid disorders.
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Accurate billing and documentation for CPT® 84481 are essential for compliance and proper reimbursement. OptiMantra’s EMR and practice management platform allows providers to seamlessly order lab tests, capture clinical indications, and integrate results into patient records. For endocrinology, primary care, and integrative clinics, OptiMantra simplifies lab workflows, reduces administrative burden, and ensures providers can focus on delivering high-quality patient care.
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