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Thyroxine (T4), Free
Test CodeLAB127
Alias/See Also
1231100162
CPT Codes
84439
Includes
THYROXINE (T4), FREE
Preferred Specimen
CLINIC COLLECTIONS: Green Litihum Heparin tube (Gel separator preferred)
Minimum Volume
CLINIC COLLECTIONS: 0.5 mL plasma
Instructions
CLINIC COLLECTIONS: Collect 0.5 ml plasma in Green Lithium Heparin tube (Gel separator preferred). Must be spun within 2 hours after collection. If no gel separator, plasma must be pulled off cells within 2 hours.
If collecting with AST, ALT, VD25, K+, or LDH, label routes to Gold/SST. Collect 1.0 mL of serum in Gold/SST. Must be spun within 2 hours after collection.
If collecting with AST, ALT, VD25, K+, or LDH, label routes to Gold/SST. Collect 1.0 mL of serum in Gold/SST. Must be spun within 2 hours after collection.
Transport Temperature
Refrigerated
Specimen Stability
Refrigerated (2°C to 8°C): 7 days
Freezer (-10°C or colder): 6 months
If testing will be delayed more than 24 hours, remove serum or plasma from the clot, red blood cells, or separator gel.
Freezer (-10°C or colder): 6 months
If testing will be delayed more than 24 hours, remove serum or plasma from the clot, red blood cells, or separator gel.
Methodology
Abbott Alinity
Reference Range
Males/Females:
0.70-1.48 ng/dL
0.70-1.48 ng/dL
Performing Laboratory
ARKADELPHIA LABORATORY CONWAY LABORATORY FORT SMITH LABORATORY LITTLE ROCK LABORATORY NORTH LITTLE ROCK LABORATORY EL DORADO LABORATORY DREW COUNTY LABORATORY
Last Updated: August 26, 2026
