Thyroid Peroxidase (TPO) Antibodies Test
A Thyroid Peroxidase (TPO) Antibodies test measures antibodies directed at thyroid peroxidase, an enzyme the thyroid uses to make its hormones. These antibodies are associated with autoimmune thyroid conditions.
About this test
Thyroid peroxidase, or TPO, is an enzyme that plays a role in producing thyroid hormones. In some people, the immune system makes antibodies against this enzyme.
The test is performed with a routine blood draw at a patient service center, where a phlebotomist collects a sample from a vein in the arm and sends it to the laboratory. People follow any preparation guidance from their ordering clinician.
Who might consider this test?
- Choosing TPO antibodies alone appeals to people and clinicians who want to focus on this single, widely used antibody marker.
Test details
| Quest code | 5081 |
|---|---|
| Methodology | Immunoassay |
| Sample type | 1 mL serum |
| Collection | Quest patient service center |
Reference range
<9 IU/mL
Reference ranges are general guidance. The range printed on your own laboratory report is the one that applies to your result.
Related tests and panels
Quest resources
Additional details
The immune side of the thyroid
Thyroid peroxidase is an enzyme the thyroid uses to build its hormones. In some people, the immune system produces antibodies aimed at this enzyme, and that is what the TPO antibodies test looks at. It describes immune activity toward the thyroid rather than the level of thyroid hormones themselves.
The presence of TPO antibodies is associated with autoimmune thyroid conditions, such as Hashimoto's thyroiditis. That link is why the marker is so widely used, but antibodies are only part of the picture and are always understood alongside other information.
Choosing TPO antibodies on their own
This test focuses on a single, well-established antibody marker rather than combining it with thyroglobulin antibodies as a broader panel would. Some people and clinicians prefer that narrower focus when TPO is the specific marker they want to look at — often after other thyroid results have prompted a closer look, or because autoimmune thyroid conditions run in the family. Because it reflects immune activity, it is commonly considered next to hormone markers like TSH and free T4.
What to expect and how results are read
The sample is collected with a quick blood draw at a patient service center, where a phlebotomist takes a small amount from a vein in the arm. Results are posted to the account once the laboratory reports them. A clinician interprets TPO antibodies in context — with symptoms, history, and other markers — rather than treating the antibody result as the whole answer.
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 the TPO antibodies test measure?
It measures antibodies directed at thyroid peroxidase, an enzyme involved in making thyroid hormones. The level of these antibodies is reported on its own in this test.
What are TPO antibodies associated with?
Their presence is associated with autoimmune thyroid conditions. Antibodies alone do not tell the whole story, so a clinician interprets them with symptoms, history, and other markers.
How is this different from an antibody panel?
This test focuses on TPO antibodies alone, while a broader panel may measure TPO antibodies together with thyroglobulin antibodies. The choice depends on what a clinician is evaluating.
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.
Is this an antibody test or a hormone test?
It is an antibody test. It reflects immune activity toward a thyroid enzyme rather than thyroid hormone levels, so it is often considered alongside hormone markers like TSH and T4.
How much does the Thyroid Peroxidase Antibodies test cost?
The cash price at Celio Health is $35. That covers the physician's order and sample collection at a Quest patient service center — no insurance is needed and there's no separate doctor's visit to pay for.