CPT® Code 84436 is used to report total thyroxine (T4) testing, a laboratory assay that measures the total amount of thyroxine hormone in the blood, including both bound and unbound fractions. Total T4 testing is commonly used to evaluate thyroid function and support the diagnosis and monitoring of thyroid disorders.
This code represents the laboratory test itself, not specimen collection, interpretation, or evaluation and management services, which may be reported separately when appropriate.
Key Facts About CPT® 84436
- Service type: Laboratory blood test
- Provider type: Physicians, laboratories, and qualified healthcare professionals
- Medical services included: Yes—total thyroxine hormone measurement
- Specimen type: Serum or plasma
- Test purpose: Thyroid function assessment
- Common clinical indications:
- Evaluation of suspected hypothyroidism or hyperthyroidism
- Follow-up of abnormal thyroid screening results
- Monitoring thyroid hormone replacement therapy
- Assessment of thyroid function during pregnancy or illness
When to Use CPT® 84436
CPT 84436 is appropriate when:
- Total T4 testing is ordered to assess overall thyroid hormone levels
- Providers need a broad measure of circulating thyroxine
- Monitoring thyroid function in diagnosed thyroid disorders
- Evaluating thyroid-related symptoms when clinically indicated
Examples:
- Ordering total T4 as part of a thyroid function panel
- Monitoring patients receiving levothyroxine therapy
- Evaluating unexplained fatigue, weight changes, or temperature intolerance
Documentation Requirements
To support CPT 84436 billing, documentation should include:
- Patient identifiers and date of service
- Clinical indication for thyroid testing
- Specimen source
- Test performed (total thyroxine, T4)
- Test result and date reported
- Ordering provider information
Accurate documentation supports compliance, appropriate reimbursement, and continuity of care.
Reimbursement and Coding Considerations
- CPT 84436 is typically covered when medically necessary
- Diagnosis coding should support thyroid-related indications
- Specimen collection may be billed separately, if allowed by payer
- Frequency limitations may apply depending on payer policy
- Often billed alongside related thyroid tests (e.g., TSH, free T4)
Always verify payer-specific laboratory testing requirements before billing.
How OptiMantra Supports Thyroid Testing
OptiMantra’s integrated EMR and practice management system streamlines documentation and billing for CPT 84436:
With OptiMantra, providers can:
- Document thyroid lab orders and results directly in the patient chart
- Track thyroid hormone trends over time
- Link results to diagnoses and treatment plans
- Support compliant, audit-ready documentation for laboratory billing workflows
- Maintain longitudinal thyroid profiles for ongoing care
By centralizing lab workflows, OptiMantra helps practices improve efficiency, support compliance, and optimize reimbursement.
Try OptiMantra for free here!
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