TSH (Thyroid-Stimulating Hormone) Test
A TSH test measures thyroid-stimulating hormone, a signal the pituitary gland sends to the thyroid. It is one of the most common first-line checks clinicians use to help evaluate how the thyroid is working.
About this test
Thyroid-stimulating hormone, or TSH, is made by the pituitary gland, a small structure at the base of the brain. Its job is to tell the thyroid how much hormone to release.
The TSH test is done with a simple blood draw at a patient service center. A phlebotomist collects a sample from a vein, usually in the arm, and the sample goes to the laboratory.
Who might consider this test?
- Often looking into symptoms that can be linked to thyroid activity
- Feeling unusually cold or warm
- Shifts in mood and energy
Test details
| Quest code | 899 |
|---|---|
| Methodology | Immunoassay |
| Sample type | 1 mL serum |
| Patient preparation | Wait at least 3 days after fluorescein dye angiography before your blood draw. If you are on hemodialysis, wait 2 weeks after angiography before your blood draw. |
| Collection | Quest patient service center |
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Additional details
What this test looks at
TSH sits at the center of a feedback loop. The pituitary gland senses how much thyroid hormone is circulating and adjusts the TSH signal to nudge the thyroid toward making more or less. Because that adjustment tends to be sensitive, TSH often shifts before other markers do, which is part of why clinicians reach for it early.
It also helps to remember what TSH is not: it describes the signal being sent to the thyroid rather than the thyroid's own hormones. That distinction is exactly why a clinician may follow a TSH result with tests that look directly at hormone output.
How it's often used alongside other thyroid tests
TSH is frequently the opening move in a thyroid evaluation. Depending on what a clinician observes and the symptoms a person describes, it may be paired with free T4 to compare the signal against the thyroid's output, or with antibody markers when an immune process is being considered. Read together, these markers offer a fuller sense of the thyroid conversation than any single one of them can on its own.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does a TSH test measure?
It measures the level of thyroid-stimulating hormone in the blood. This hormone comes from the pituitary gland and reflects the signal being sent to the thyroid rather than the thyroid's hormones themselves.
Why is TSH often the first thyroid test ordered?
The pituitary adjusts TSH sensitively in response to thyroid output, so a single TSH result can help a clinician decide whether the thyroid picture needs a closer look with additional markers.
How is the sample collected?
Through 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.
Do I need to prepare for this test?
Wait at least 3 days after fluorescein dye angiography before your blood draw. If you are on hemodialysis, wait 2 weeks after angiography before your blood draw. This is the preparation Quest publishes for this test; if your clinician gives you different instructions, follow theirs.
Is TSH ever measured together with other markers?
Yes. Clinicians often pair TSH with free T4 or other thyroid markers to get a fuller view. TSH reflects the pituitary's signal, while thyroid hormones reflect the gland's actual output.
How much is a TSH test?
$19, paid once at checkout. The price includes the physician's order this test requires and sample collection at a Quest patient service center.