Thyroid Peroxidase Antibodies (TPOAb)
It checks for autoimmune thyroid antibodies that can explain thyroid symptoms and predict future hypothyroidism, with easy ordering and Quest labs via Vitals Vault.
This panel bundles multiple biomarker tests in one order—your report explains how results fit together.
Thyroid peroxidase antibodies (TPOAb) are immune proteins that can show whether your immune system is targeting your thyroid. This test does not measure thyroid hormone directly, but it can explain why your thyroid levels are drifting or why symptoms persist even when “standard” thyroid labs look borderline.
A positive TPOAb result is most often linked with Hashimoto’s thyroiditis (autoimmune hypothyroidism), and it can also be seen in other thyroid conditions. Knowing your antibody status helps you and your clinician decide what to monitor next and how often to recheck.
Because antibody levels can fluctuate, the most useful approach is usually to interpret TPOAb alongside thyroid function tests such as TSH and free T4, and then track trends over time rather than reacting to a single number.
Do I need a Thyroid Peroxidase Antibodies test?
You may want a TPOAb test if you have symptoms that could fit a thyroid problem—such as fatigue, cold intolerance, constipation, dry skin, hair thinning, weight change, brain fog, or menstrual cycle changes—especially if your TSH is high, rising over time, or “high-normal” and you still do not feel like yourself.
This test is also commonly used when you have an enlarged thyroid (goiter), thyroid nodules, or a strong family history of autoimmune disease (including autoimmune thyroid disease). If you are planning pregnancy, are pregnant, or recently postpartum, antibody status can be clinically relevant because autoimmune thyroiditis can emerge or shift during these periods.
If you already have hypothyroidism and take levothyroxine, TPOAb is not usually a dose-adjustment test. However, it can clarify the underlying cause and can help guide what to monitor (for example, whether to also check other antibodies or to follow thyroid function more closely).
Your result is one piece of the picture. Testing supports clinician-directed care and follow-up planning, and it is not a standalone diagnosis of any condition.
This is a blood immunoassay performed in a CLIA-certified laboratory; results should be interpreted with your symptoms and thyroid function tests, not used alone to self-diagnose.
Lab testing
Order Thyroid Peroxidase Antibodies testing
About 1 week
Schedule online — results typically within a week
Clear next steps
Guidance included, with follow-up care available
HSA / FSA
Eligible for pre-tax health spending accounts
Get this test with Vitals Vault
Vitals Vault lets you order Thyroid Peroxidase Antibodies testing directly, then complete your blood draw at a participating lab location. You get a clear lab report you can share with your clinician, plus an easy way to keep results organized for trend tracking.
If your TPOAb comes back positive or you are trying to understand a borderline thyroid pattern, PocketMD can help you prepare the right follow-up questions. For many people, the next step is pairing antibodies with thyroid function markers (TSH and free T4) and, when appropriate, additional thyroid antibodies.
You can also use Vitals Vault to recheck at a sensible interval (often months, not days) so you can see whether your thyroid function is stable, improving, or drifting toward hypothyroidism.
- Order online and complete your draw at a participating lab location
- Results you can download and share with your clinician
- PocketMD helps you interpret patterns and plan follow-up
Key benefits of Thyroid Peroxidase Antibodies testing
- Helps identify autoimmune thyroiditis as a likely cause of thyroid symptoms or abnormal TSH.
- Clarifies your risk of developing hypothyroidism, especially when TSH is trending upward.
- Adds context when thyroid hormone levels are borderline and symptoms do not match the numbers.
- Supports pregnancy and postpartum thyroid monitoring decisions when autoimmune thyroid disease is a concern.
- Guides which companion tests are most useful next (TSH, free T4, thyroglobulin antibodies, and sometimes TRAb).
- Helps you and your clinician distinguish “thyroid inflammation” patterns from non-thyroid causes of fatigue or weight change.
- Creates a baseline you can track over time, using PocketMD to translate results into a practical follow-up plan.
What is Thyroid Peroxidase Antibodies (TPOAb)?
Thyroid peroxidase (TPO) is an enzyme your thyroid uses to make thyroid hormones. In some people, the immune system mistakenly targets this enzyme and produces thyroid peroxidase antibodies (TPOAb).
A TPOAb test measures how strongly your immune system is reacting to TPO. A positive result suggests autoimmune thyroid disease is present or more likely, most commonly Hashimoto’s thyroiditis. Over time, autoimmune activity can damage thyroid tissue and reduce hormone production, which can lead to hypothyroidism.
TPOAb is not the same thing as thyroid hormone. You can have positive antibodies with normal thyroid function, especially early on, and you can also have hypothyroidism with low or negative antibodies. That is why TPOAb is usually interpreted alongside thyroid function tests and your clinical picture.
How TPO antibodies relate to Hashimoto’s thyroiditis
Hashimoto’s thyroiditis is an autoimmune condition where immune activity gradually impairs the thyroid’s ability to produce hormone. TPOAb is one of the most common antibodies seen in Hashimoto’s, and a positive result often supports that diagnosis when paired with an elevated TSH and/or low free T4.
Can TPOAb be positive without symptoms?
Yes. Some people have detectable antibodies for years before thyroid hormone levels change. In that situation, the test is most useful for risk assessment and deciding how often to monitor TSH and free T4, rather than for immediate treatment decisions.
What this test does not tell you
TPOAb does not measure how much thyroid hormone your body is making today, and it does not diagnose the severity of hypothyroidism. It also does not rule out other thyroid conditions, which may require different antibody tests or imaging depending on your symptoms and exam.
What do my Thyroid Peroxidase Antibodies results mean?
Low or negative TPOAb
A low or negative result means the lab did not detect a significant immune response to thyroid peroxidase. This makes Hashimoto’s thyroiditis less likely, but it does not completely rule it out, especially if you have clear hypothyroid labs or ultrasound findings. If your TSH or free T4 is abnormal, your clinician may still look for other causes, including other thyroid antibodies or non-thyroid contributors to symptoms.
In-range TPOAb
An in-range result is typically interpreted similarly to a negative result: there is no strong evidence of TPO-directed autoimmunity on this test. If you feel well and your thyroid function tests are normal, this is generally reassuring. If symptoms persist, the next step is usually to focus on thyroid function (TSH and free T4) and broader contributors such as iron status, vitamin levels, sleep, stress, and medications.
High or positive TPOAb
A high result suggests autoimmune thyroid disease is present or more likely, most often Hashimoto’s thyroiditis. The key follow-up question is whether your thyroid function is currently affected, which is assessed with TSH and free T4 (and sometimes free T3). If your thyroid function is normal, a positive TPOAb still matters because it can increase the chance of developing hypothyroidism over time, so periodic monitoring is often recommended.
Factors that influence TPOAb results
Different labs and assay methods can use different reference ranges, so it helps to compare your result to the range on your report and to trend results at the same lab when possible. Antibody levels can fluctuate and do not always track symptom severity, so a single value is less informative than the overall pattern with TSH and free T4. Pregnancy and the postpartum period can shift immune activity and thyroid function, which may change antibody levels and monitoring needs. Certain medications and supplements can affect thyroid testing broadly (for example, biotin can interfere with some immunoassays), so tell your clinician what you take before retesting.
What’s included
Frequently Asked Questions
What is a normal range for thyroid peroxidase antibodies (TPOAb)?
“Normal” depends on the lab and the specific assay, so the most accurate reference is the range printed on your report. Many labs report TPOAb as negative/in-range below a cutoff and positive above it. If you are comparing past results, try to use the same lab method so changes reflect your biology rather than a different reference range.
Does a positive TPO antibody test mean I have Hashimoto’s?
A positive TPOAb result strongly supports autoimmune thyroid disease, and Hashimoto’s thyroiditis is the most common reason. However, diagnosis usually considers your thyroid function tests (TSH and free T4), symptoms, physical exam, and sometimes ultrasound. Some people have positive antibodies with normal thyroid hormone levels, especially early on.
Can TPO antibodies be high if my TSH is normal?
Yes. Antibodies can appear before thyroid hormone production changes. In that situation, the practical next step is usually periodic monitoring of TSH and free T4, plus symptom tracking, rather than treating based on antibodies alone.
Should I retest TPO antibodies, and how often?
Retesting frequency depends on why you tested. If the goal is to assess autoimmune risk, many clinicians focus more on trending TSH and free T4 than repeatedly measuring TPOAb, because antibody levels can fluctuate and do not always correlate with symptoms. If you do retest, it is typically done months later (often 6–12 months) or when your thyroid function changes.
Do I need to fast for a TPO antibody blood test?
Fasting is not usually required for TPOAb testing. If your blood draw includes other tests that do require fasting (such as certain lipid or glucose tests), follow the instructions for the full panel you ordered.
What other thyroid tests should I get with TPO antibodies?
Common companion tests include TSH and free T4 to assess current thyroid function. Thyroglobulin antibodies (TgAb) can add information about thyroid autoimmunity, and in specific situations your clinician may consider TSH receptor antibodies (TRAb) when hyperthyroidism or Graves’ disease is suspected. The right combination depends on your symptoms, pregnancy status, and current thyroid medication use.