| Ordering Code | 366 |
|---|---|
| Test Name | T4, Free |
| Alias | Free T4 Free Thyroxine |
| Preferred Specimen | Serum |
| Preferred Container | SST (Gold) |
| Other Specimen/Container | Serum in Plain (Red), Plasma in Lithium Heparin (Green-PST), Plasma in Lithium Heparin (Dark Green-PP No Gel) |
| Optimum Volume | 1 mL |
| Handling Instructions | All specimen types must be centrifuged within 2 hours of collection. If no gel separation present in tube and testing is delayed, plasma/serum is aliquoted from cells within 2 hours of collection Keep tubes stoppered at all times. |
| Transport Requirements | Oahu: Refrigerated Airline: Refrigerated |
| Specimen Stability | Ambient: 8 Hours Refrigerated: 2 Days Frozen: 30 Days Frozen samples should be thawed only once DO NOT use frost-free freezers. |
| Rejection Criteria | Specimen older than stability limits, Grossly hemolyzed, Insufficient quantity, Grossly lipemic |
| Avail. Stat | NO |
| Analytic Time | 1 Day |
| Methodology | Chemiluminescent Immunoassay - Two-step competitive |
Reference range(s)
The reference ranges listed below are valid on this date of November 3, 2025.
| Component | Age | Male Norm | Male Critical Low | Male Critical High | Female Norm | Female Critical High | Female Critical Low | Units | Add'l info |
|---|---|---|---|---|---|---|---|---|---|
| T4, Free | ALL | 0.70-1.80 | 0.70-1.80 | ng/dL |
