T3 Uptake

Cleveland Heartlab T, Test

CPT Code: 84479
Order Code: C1372
ABN Requirement: No
Synonyms: T3U; Hanolsky Uptake Test; Resin Uptake; T3 (Triiodothyronine); T3 Index; T3 resin; T3, Resin Uptake; T3 UP; T3RU; Tri-iodothyronine UPTAKE; Triiodothyronine, Resin Uptake (T3); Triiodothyronine
Specimen: Serum
Volume:  1.0 mL
Minimum Volume:  0.5 mL
Container: Gel-barrier tube (SST, Tiger Top)


  1. Collect and label sample according to standard protocols.
  2. Gently invert tube 10 times immediately after draw. Do not shake.
  3. Allow blood to clot 30 minutes.
  4. Centrifuge for 10 minutes.

Transport:   Store serum at 2°C to 8°C after collection and ship the same day per packaging instructions included with the provided shipping box.


Ambient (15-25°C): 7 days
Refrigerated (2-8°C): 10 days
Frozen (-20°C): 28 days

Causes for Rejection: Specimens other than serum; improper labeling; samples not stored properly; samples older than stability limits

Methodology: Immunoassay (IA)

Turn Around Time: 3-4 days

Reference Range:

Age %
All Ages 22-35

Clinical Significance: The T3 uptake assay is a measure of available thyroid hormone binding sites and should be interpreted with thyroxine levels.

Additional Information: Decreased: Pregnancy, estrogens, hyperproteinemia, acute intermittent porphyria; Increased: Androgens, hyperproteinemia, stress, acute liver disease

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.