Total T4

CPT Code


Specimen Type


Container Type

Serum Separator Tube (SST)/Yellow


Room Temperature, 8 hours; 2-8°C, 24 hours; -20°C, > 24 hours

Handling Instructions

Allow to clot for 30 mins, centrifuge within 2 hours

Clinical Notes

T4 or thyroxine is the major hormone made in your thyroid gland. The name T4 derives from the fact that the thyroxine molecule has four iodine atoms attached to it. Thyroid hormones are critical to brain development during infancy and for many essential body processes during adulthood. Usually, your body has large stores of T4 circulating in your blood. However, most of your circulating T4 is bound to proteins and is not available for immediate use by the body.