Thyroid Antibodies (TPO + Thyroglobulin)
Detect autoimmune thyroid conditions like Hashimoto's disease or Graves' disease by measuring antibodies that may be attacking thyroid tissue.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
What this test measures
This test measures two antibodies that the immune system produces when it mistakenly targets normal thyroid components: thyroid peroxidase antibodies (TPO Ab) and thyroglobulin antibodies (TgAb). Thyroid peroxidase is an enzyme the thyroid gland requires to incorporate iodine into thyroglobulin during the production of T3 and T4 hormones. Thyroglobulin is the precursor protein from which the thyroid manufactures those same hormones.
When the immune system generates antibodies against either of these proteins, it indicates autoimmune activity directed at the thyroid. The most common cause of elevated thyroid antibodies is Hashimoto's thyroiditis, an autoimmune condition that gradually damages the thyroid and frequently leads to hypothyroidism. Elevated antibodies can also occur in Graves' disease and, less commonly, in other autoimmune disorders. In the context of thyroid cancer monitoring, thyroglobulin antibodies are clinically important because they can interfere with thyroglobulin measurements, the primary marker used to track cancer recurrence after treatment. Detecting these antibodies allows healthcare providers to account for that interference and adjust monitoring accordingly.
What's included
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals experiencing symptoms that could suggest thyroid problems, such as unexplained fatigue, weight changes, hair loss, mood changes, or temperature sensitivity
- Those with a family history of autoimmune thyroid conditions like Hashimoto's disease or Graves' disease, as these conditions often run in families
- People who have been diagnosed with other autoimmune conditions such as type 1 diabetes, rheumatoid arthritis, or celiac disease, which may increase thyroid antibody risk
- Individuals with abnormal TSH or thyroid hormone test results who need further evaluation to determine if an autoimmune process is involved
- Women who are pregnant or planning pregnancy and have a personal or family history of thyroid disease, as thyroid antibodies can affect pregnancy outcomes
- Those being monitored for thyroid cancer recurrence after treatment, as thyroglobulin antibodies can interfere with tumor marker testing
What to expect
Preparation
No fasting is required for this test. Individuals should inform their healthcare provider about biotin supplements, as high doses may interfere with test results and should typically be stopped 72 hours before testing. No other special preparation is needed.
Sample Type
A simple blood draw from a vein in the arm, similar to routine blood work
Collection
The blood sample collection typically takes just a few minutes. A healthcare professional will clean the area, insert a small needle to draw blood into a collection tube, and apply a bandage afterward.
Turnaround
Results are typically available within 1-3 business days after the laboratory receives the sample
Understanding your results
Results are reported in international units per milliliter (IU/mL). TPO antibodies are generally considered normal below approximately 35 IU/mL, and thyroglobulin antibodies below approximately 20 IU/mL, though exact cutoffs vary by laboratory. The absolute antibody concentration matters for interpretation, and tracking levels over time using the same assay provides valuable information about whether autoimmune activity is stable, increasing, or declining. Healthcare providers evaluate thyroid antibody results alongside TSH, free T4, free T3, and clinical symptoms to assess whether immune-mediated thyroid damage is occurring and whether it is affecting hormone production.
| Population | Reference Range | Notes |
|---|---|---|
| Adults | TPO Antibodies: < 35 IU/mL; Thyroglobulin Antibodies: < 20 IU/mL | Values above these thresholds may indicate autoimmune thyroid activity |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
It is not possible for thyroid antibodies to be too low. Normal or undetectable levels of these antibodies typically indicate that an autoimmune process is not currently affecting the thyroid gland. However, it's worth noting that some individuals with autoimmune thyroid conditions may have antibody levels that are too low to detect, particularly in early stages of disease. Normal antibody levels combined with normal thyroid function tests generally suggest that autoimmune thyroid disease is unlikely, though other causes of thyroid dysfunction should still be considered if symptoms are present.
What does a “High” result mean?
Elevated TPO antibodies may indicate Hashimoto's disease if TSH levels are also high, or may suggest an increased risk of developing hypothyroidism later in life if thyroid function is currently normal. TPO antibodies are present in roughly 90% of people with Hashimoto's thyroiditis and in half to three-quarters of people with Graves' disease. Elevated thyroglobulin antibodies may also indicate Hashimoto's disease. It's important to note that 10-15% of people with no thyroid disorder can have raised TPO antibodies, and high TPO antibodies may increase the risk of developing a thyroid disorder in the future. Having elevated antibodies doesn't necessarily mean immediate thyroid dysfunction, but indicates that the immune system is showing activity against thyroid tissue.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. Your thyroid antibody test results remain completely confidential and are <u>not reported to your doctor</u> unless you choose to share them. This testing is conducted with the highest privacy standards - your results are <u>not part of your medical records</u> and will <u>not appear on insurance statements</u> or explanations of benefits. The laboratory follows strict confidentiality protocols, ensuring that your health information is protected and not shared with employers, insurance companies, or other third parties without your explicit consent. You maintain full control over who has access to your test results, allowing you to make informed health decisions in a private, judgment-free environment. Many individuals appreciate the discretion this testing provides when exploring potential autoimmune thyroid conditions or monitoring their thyroid health without involving their regular healthcare system. No doctor visit is required to order this test, giving you the freedom to take charge of your health screening on your own terms.
Frequently asked questions
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Related articles
The Complete Guide to Thyroid Testing: Which Test Do You Actually Need?
Read ArticleWhat Does a High TSH Mean? (And What to Do Next)
Read ArticleHashimoto's Disease: The Autoimmune Condition Your Doctor Might Miss
Read ArticleLast reviewed: April 2026
CPT Code: 86376, 86800
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
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