TSH and Free T4 Test
A TSH and Free T4 test brings two core thyroid markers together in one order: thyroid-stimulating hormone and free thyroxine. Pairing them lets clinicians view the pituitary signal and the thyroid's output side by side.
About this test
TSH, thyroid-stimulating hormone, is the signal the pituitary gland sends to the thyroid. Free T4 is the unbound, active-available form of thyroxine, the main hormone the thyroid releases. This pairing puts the two together because they describe different parts of the same system: TSH reflects the signal going in, while free T4 reflects the hormone output coming back. Seen together, they give a fuller sense of how the thyroid conversation is relating.
The test is collected with a routine blood draw at a patient service center, where a phlebotomist takes a sample from a vein in the arm and sends it to the laboratory. People follow any preparation guidance from their ordering clinician. Because the two markers are meant to be read together, a clinician interprets them as a pair, in the context of symptoms, history, and the person's overall picture.
Who commonly orders it
People who order TSH with free T4 often want a step beyond a single TSH reading, pairing the pituitary signal with the thyroid's actual output for a more complete view. Some are following up on an earlier result, exploring symptoms that may be linked to thyroid activity, or keeping an eye on thyroid care over time. The pairing appeals to those who want both sides of the thyroid conversation in one draw.
What pairing these two markers offers
TSH and free T4 describe opposite ends of the same conversation. TSH is the signal the pituitary sends toward the thyroid, while free T4 is the unbound, active-available form of the hormone the thyroid sends back. On its own, either marker tells only half the story; put together, they let a clinician see how the signal going in lines up with the output coming out.
That is why this pairing is a common step beyond a single TSH reading — it adds the hormone side of the picture without expanding to a full panel.
How the two are read as a pair
Because they are meant to be interpreted together, a clinician looks at TSH and free T4 side by side rather than one after the other. The way the two relate can be more informative than either value in isolation. As always, that reading happens in context, with symptoms, history, and any other findings taken into account.
What to expect at your visit
Both markers come from one quick draw. A phlebotomist collects a small sample from a vein in the arm during a short, walk-in visit at a patient service center, and the laboratory measures TSH and free T4 from that same sample. Results are posted to the account together, ready to review and share with a clinician. Because the two are meant to be read as a pair, seeing them arrive side by side reflects how they are intended to be interpreted.
Your results
Results will be emailed securely to you as a PDF.
Order TSH and Free T4 in a panel
TSH and Free T4 isn't sold on its own online — it's included in these physician-ordered panels:
- ✓ Physician order included · results in 24–72 hrs
Prefer just this single marker? Request it →
Prefer a fuller panel?
A curated bundle groups this test with the markers clinicians most often review alongside it — often better value than single tests.
Frequently asked questions
What does the TSH and Free T4 test measure?+–
It measures two markers together: TSH, the pituitary's signal to the thyroid, and free T4, the unbound, active-available form of the thyroid's main hormone.
Why are TSH and free T4 measured together?+–
TSH reflects the signal going to the thyroid, while free T4 reflects the thyroid's hormone output. Looking at both gives a clinician a fuller view of how the two relate.
How is free T4 different from total T4?+–
Free T4 measures only the unbound portion of thyroxine, which is less affected by carrier proteins. Total T4 counts both bound and unbound hormone.
How is the sample collected?+–
With a routine blood draw at a patient service center. A phlebotomist takes a small sample from a vein in the arm and sends it to the laboratory.
Are the two markers read separately?+–
They are meant to be interpreted together as a pair, in the context of symptoms, history, and the person's overall picture, rather than one on its own.