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v1.0.0
ICD-10 Guide
DiagnosesFree T4

Free T4

ICD-10 Coding for Free T4 Test(E05.90, E03.9)

PRIMARY SPECIALTYEndocrinology
COMPLEXITYHigh
LAST UPDATED09/15/2025
Sam Tuffun, PT, DPT
Physical Therapist | Medical Coding & Billing Contributor

Diagnosis Overview

What is Free T4?
Essential facts and insights about Free T4 Test

Key Clinical Considerations:

  • Symptoms of hyperthyroidism or hypothyroidism
  • Elevated or decreased Free T4 levels in serum
  • Goiter or thyroid nodules on physical examination

Clinical Information

Clinical Criteria & Documentation Requirements

  • Patient history including symptoms and medication use
  • Laboratory results for Free T4 and TSH levels
  • Physical exam findings related to thyroid function

Coding Guidelines

Usage Guidelines & Examples

  • Follow guidelines for distinguishing between hyperthyroidism and hypothyroidism.
  • Common errors include misclassifying thyroid conditions.

Code Exclusions

Important Exclusions

  • Conditions like thyroiditis or thyroid cancer
  • Alternative codes for related endocrine disorders

Related ICD-10 Codes

Primary Codes
E03.9
Hypothyroidism, unspecified
E05.9
Thyrotoxicosis, unspecified
Ancillary Codes
R94.6
Differential Codes
E03.9
T4
is low and TSH is elevated, indicating hypothyroidism.
E05.90
T4
is elevated and TSH is suppressed, indicating hyperthyroidism.

Related CPT Codes

CPT codes will be available in a future update.

Specialty Focus

Primary Specialty

Endocrinology

Specialty Applications

  • Adults and children with suspected thyroid disorders
  • Endocrinology clinics and primary care settings

Coding Complexity

High Complexity

This diagnosis requires careful attention to:

  • Comprehensive clinical documentation
  • Accurate code selection based on clinical criteria
  • Proper exclusion considerations
  • Specialty-specific coding guidelines

Documentation

Documentation Templates

Billing Information

Billing Considerations

  • Ensure proper documentation for billing
  • Verify code specificity requirements
  • Check for any additional codes needed
  • Review payer-specific guidelines

Common Issues

  • Insufficient clinical documentation
  • Incorrect code selection
  • Missing supporting diagnoses
  • Timing and frequency documentation

Frequently Asked Questions

Documentation requirements?

Include patient history, lab results, and physical exam findings.

Billing considerations?

Ensure accurate coding based on lab results and clinical findings.