Lab services are not currently available. We're working to bring Feelrx Labs online soon — everything below is a preview of what's coming.
Quest / Thyroid Function
T4 Free (FT4)
This test measures the unbound, biologically active form of thyroxine (T4) circulating in the blood. Unlike total T4, it reflects the portion not attached to proteins and available for use by tissues. Free T4 is a key marker of thyroid function and helps assess how much hormone is available to act on the body.
Coming Soon
What this lab measures
This test measures the unbound, biologically active form of thyroxine (T4) circulating in the blood. Unlike total T4, it reflects the portion not attached to proteins and available for use by tissues. Free T4 is a key marker of thyroid function and helps assess how much hormone is available to act on the body.
How testing works
Order online
Choose your marker and add a brief medical history so your result has context from the first draw.
Visit a partner lab
Take your order to a certified Quest location for a short blood draw.
Clinician review
A licensed clinician reviews your result and shares clear interpretation with next steps.
FAQ
After ordering, visit a certified Quest partner location for a short blood draw. No insurance is required.
Feelrx / Start here
Know your baseline.
Order a panel online, draw at a certified partner lab, and receive a clear clinician review.
Coming Soon