Assay of free thyroxine

Procedure Information

What is an Assay of Free Thyroxine?

An Assay of Free Thyroxine (also referred to as Free T4 or FT4) is a blood test used to measure the amount of a thyroid hormone, thyroxine, in the bloodstream.

Why Would I Get an Assay of Free Thyroxine?

A doctor may order an Assay of Free Thyroxine to check for possible thyroid disorders, such as an overactive thyroid (hyperthyroidism) or an underactive thyroid (hypothyroidism). This test may also be used to evaluate the effectiveness of thyroid medications or to determine the cause of high thyroid-stimulating hormone (TSH) levels.

What Happens During an Assay of Free Thyroxine?

The Assay of Free Thyroxine procedure involves a sample of blood being drawn and sent to a lab for analysis. Your doctor may provide instructions to prepare and/or modify medication doses before the procedure.

What to Expect After an Assay of Free Thyroxine?

Once the lab has analyzed the sample, the results will be sent to your doctor. Your doctor will interpret the results and use them to help diagnose and/or treat any thyroid disorder.

Conclusion

An Assay of Free Thyroxine is a blood test used to measure the amount of hormone thyroxine in the bloodstream. It is conducted to assess possible thyroid disorders and to evaluate the effectiveness of medications. The procedure involves a blood draw and the results are reported to the doctor. The doctor will interpret the results and use them to diagnose and/or treat any thyroid issue.