Special instruction: This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to stop biotin consumption at least 72 hours prior to the collection of a sample.
Preparation instructions: Fasting prior to blood draw recommended (per LabCorp)
Description: A test that measures levels of thyroxine, also known as T4, in the blood. Typically used to evaluate hyper- or hypothyroidism.
Turnaround time: Expected turnaround is within one day, although this may vary depending on other tests ordered for the same blood draw, and expected variation with LabCorp testing.
Also known as:
- Total T4
- T4, Total