Lab comparisonCPT 84439
Free T4: Quest vs LabCorp vs BioReference, tube, code & requirements
Measures unbound thyroxine in blood. This page shows collection requirements for all three major reference labs in one view, so you don’t have to cross-check three portals.
Always verify against your lab’s current collection manual before drawing.
Every value on this page is verified by a nurse practitioner in active clinical practice, not scraped from an automated source.
| Requirement | Quest Diagnostics | LabCorp | BioReference |
|---|---|---|---|
| Test code | 902 | 001974 | 0843900 |
| Primary tube | Red Top or Gold SST | Gold SST | Red Top |
| Specimen type | Serum | Serum | Serum |
| Patient prep | None | None | None |
Frequently asked questions
What is the Quest Diagnostics order code for Free T4?
The Quest Diagnostics order code for Free T4 is 902.
What tube color does LabCorp use for Free T4?
LabCorp uses a Gold SST for Free T4.
Does Free T4 require fasting?
No fasting is required for Free T4.
Data provenance
Source: Quest Diagnostics specimen collection manual, LabCorp directory of services, and BioReference laboratory collection guide.
Verified by: a licensed nurse practitioner in active clinical practice. Values are reviewed against each lab’s published collection requirements. Always confirm against your lab’s current manual before drawing.
Need the full lookup, not just a comparison?
No login · Zero PHI · Clinician-verified · Quest + LabCorp + BioReference.