Thyroid Peroxidase (TPO) and Thyroglobulin (Tg) Antibodies Biomarker Testing
It checks thyroid autoantibodies linked to Hashimoto’s and Graves’ risk, with clear next steps and convenient Quest lab access via Vitals Vault.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
This test looks for two immune proteins (antibodies) that commonly show up when your immune system is targeting your thyroid: thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb).
These antibodies do not measure how much thyroid hormone you are making today. Instead, they help explain why your thyroid labs may be shifting, why symptoms might not match a “normal” TSH, or why you are at higher risk of developing thyroid dysfunction over time.
Because antibody levels can stay elevated for years, the most useful question is usually not “Is it positive?” but “How does this fit with my TSH, free T4, symptoms, and trend over time?”
Do I need a Thyroid Peroxidase And Thyroglobulin Antibodies test?
You may want TPOAb and TgAb testing if you have symptoms that could fit thyroid dysfunction—such as fatigue, feeling unusually cold, weight change, constipation, hair thinning, palpitations, anxiety, or menstrual changes—especially when your screening test (often TSH) is borderline, fluctuating, or doesn’t match how you feel.
This test is also commonly ordered when you have a goiter (enlarged thyroid), thyroid nodules, a strong family history of autoimmune thyroid disease, other autoimmune conditions (such as type 1 diabetes or celiac disease), or thyroid changes after pregnancy. In these situations, antibodies can help clarify whether an autoimmune process like Hashimoto’s thyroiditis is likely.
If you are pregnant, trying to conceive, or have had pregnancy loss, antibody status can be clinically relevant because thyroid autoimmunity can increase the chance of thyroid function changes during and after pregnancy. Your clinician may use antibody results to decide how closely to monitor TSH and free T4.
Testing supports clinician-directed care and follow-up planning, but it does not diagnose a condition by itself. Your result is most meaningful when interpreted alongside thyroid function tests and your medical history.
These antibody tests are run in CLIA-certified laboratories; results should be interpreted with your clinician and are not a standalone diagnosis.
Lab testing
Order thyroid antibody testing and schedule your draw when it works for you.
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
Vitals Vault lets you order thyroid antibody testing without a referral and complete your blood draw at a participating Quest location. That can be helpful when you are comparing options, confirming a prior result, or building a clearer thyroid picture before a clinician visit.
After your results are ready, you can use PocketMD to review what a positive or negative antibody result typically means, what companion labs to consider (like TSH and free T4), and when a retest is reasonable based on your situation.
If your results suggest autoimmune thyroid risk, you can use Vitals Vault to recheck trends over time or add related thyroid markers so you and your clinician can make decisions with more context rather than a single data point.
- Order online and draw at a Quest location
- PocketMD guidance for next-step questions to bring to your clinician
- Easy retesting to track trends over time
Key benefits of Thyroid Peroxidase And Thyroglobulin Antibodies testing
- Helps identify autoimmune thyroid disease risk even before thyroid hormone levels clearly change.
- Adds context when TSH is borderline, fluctuating, or doesn’t match your symptoms.
- Supports earlier monitoring plans for people with family history or other autoimmune conditions.
- Helps clarify whether hypothyroidism is likely due to Hashimoto’s thyroiditis.
- Guides pregnancy and postpartum monitoring when thyroid autoimmunity is a concern.
- Improves interpretation of thyroid nodules or goiter workups when paired with imaging and thyroid function tests.
- Creates a baseline so you can track antibody and thyroid-function trends over time with repeat testing.
What is Thyroid Peroxidase And Thyroglobulin Antibodies?
Thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb) are proteins made by your immune system that can bind to parts of your thyroid. When these antibodies are present, it suggests your immune system is reacting to thyroid tissue, which is common in autoimmune thyroid disease.
TPO (thyroid peroxidase) is an enzyme your thyroid uses to help make thyroid hormones. Thyroglobulin is a protein inside the thyroid that serves as a building block and storage form for thyroid hormone production. Antibodies against either target can be a sign of ongoing thyroid inflammation (thyroiditis), even if your thyroid hormone levels are still within the lab reference range.
A positive antibody result does not automatically mean you need treatment. Many people with antibodies have normal thyroid function for years, while others gradually develop hypothyroidism or, less commonly, hyperthyroidism depending on the underlying condition and timing.
How these antibodies relate to Hashimoto’s and Graves’
TPOAb is most strongly associated with Hashimoto’s thyroiditis, the most common cause of hypothyroidism in iodine-sufficient regions. TgAb can also be present in Hashimoto’s and other autoimmune thyroid conditions. Graves’ disease is more specifically linked to TSH receptor antibodies (TRAb/TSI), but TPOAb and TgAb can still be positive in Graves’ or in people who later transition between hyperthyroid and hypothyroid phases.
What the test does (and does not) tell you
This test tells you about immune activity directed at the thyroid, not how much hormone your thyroid is producing today. To understand current thyroid function, you typically need TSH plus free T4 (and sometimes free T3). Antibody testing is most useful for explaining the “why” behind abnormal or changing thyroid function and for planning monitoring.
What do my Thyroid Peroxidase And Thyroglobulin Antibodies results mean?
Low or negative antibody levels
A low or negative TPOAb and TgAb result means these common thyroid antibodies were not detected or are below the lab’s cutoff. This lowers the likelihood of Hashimoto’s thyroiditis, but it does not completely rule out thyroid disease. Thyroid symptoms can still come from non-autoimmune causes, and some autoimmune thyroid cases are antibody-negative. If your TSH or free T4 is abnormal, your clinician may still evaluate other causes or order additional tests.
In-range results (within the lab reference interval)
When antibody values fall within the reference interval, it usually suggests no clear evidence of thyroid autoimmunity at the time of testing. If you have symptoms, the next step is often to focus on thyroid function markers (TSH and free T4) and other contributors like iron status, vitamin B12, sleep, stress, or medications. If you are pregnant, postpartum, or have a strong family history, your clinician may still monitor thyroid function periodically because risk is influenced by more than one lab value.
High or positive antibody levels
A high or positive TPOAb and/or TgAb result suggests your immune system is reacting to thyroid tissue. This is common in Hashimoto’s thyroiditis and can appear before TSH rises or free T4 falls, which is why antibody positivity often leads to closer monitoring over time. The most important follow-up is to interpret the antibodies alongside TSH and free T4 to see whether thyroid function is currently normal, trending, or already abnormal. Antibody levels can fluctuate and do not always correlate with symptom severity, so decisions are usually based on thyroid function and clinical context rather than antibody number alone.
Factors that influence thyroid antibody results
Different labs and assay methods use different cutoffs, so “positive” and “negative” should be read using the reference range on your report. Antibody levels may change during pregnancy and postpartum, and they can vary over time even without treatment. Autoimmune conditions can cluster, so having another autoimmune diagnosis can increase the chance of thyroid antibodies. Some medications and immune-modulating therapies may affect antibody levels, and recent thyroid inflammation can temporarily shift results, which is why trend and timing matter.
What’s included
- Thyroid Peroxidase Antibodies
- Thyroglobulin Antibodies
Frequently Asked Questions
Do I need to fast for TPO and thyroglobulin antibody tests?
Fasting is not usually required for thyroid antibody testing. If your blood draw includes other tests (like lipids or glucose), fasting instructions may come from those tests instead.
What is a normal range for TPO antibodies and Tg antibodies?
“Normal” depends on the lab and the specific assay, so you should use the reference interval printed next to your result. Many reports show antibodies as negative/borderline/positive based on a cutoff rather than a single universal number.
Can you have Hashimoto’s with normal TSH?
Yes. Many people have positive TPOAb (and sometimes TgAb) while TSH and free T4 are still within range. In that situation, antibodies suggest higher future risk, and clinicians often monitor thyroid function over time rather than treat immediately.
If my antibodies are positive, does that mean I need thyroid medication?
Not necessarily. Treatment decisions are usually based on thyroid function (TSH and free T4), symptoms, pregnancy status, and clinical history. Antibodies help explain cause and risk, but they are not the only factor that determines whether medication is appropriate.
How often should thyroid antibodies be rechecked?
Many clinicians do not recheck antibodies frequently because levels can stay elevated for years and may not track symptoms. Retesting may be reasonable if your clinical picture changes, if you are planning pregnancy or are postpartum, or if your clinician is using a baseline to support a monitoring plan. More commonly, TSH and free T4 are trended.
What other thyroid tests should I consider with TPOAb and TgAb?
TSH and free T4 are the usual companions to understand current thyroid function. Depending on your situation, your clinician may also consider free T3, TSH receptor antibodies (TRAb/TSI) if hyperthyroidism is suspected, and imaging such as thyroid ultrasound when nodules or goiter are present.
Can thyroid antibodies cause symptoms even if my thyroid hormones are normal?
Antibodies themselves are a sign of immune activity, and some people feel unwell during inflammatory phases even before hormone levels change. However, symptoms like fatigue and brain fog have many causes, so it is important to interpret antibody results alongside thyroid function tests and a broader health review.