Quick answer: in the thyroglobulin antibodies normal range, a negative result means no antibodies to thyroglobulin were found (MedlinePlus). Mayo Clinic Laboratories reports a reference value of under 4.0 IU/mL, and notes that a cutoff of under 1.8 IU/mL may suit better when the goal is to spot antibody interference with thyroglobulin testing. Cutoffs depend on the assay, so use your own lab's. A positive TgAb can go with Hashimoto thyroiditis or Graves disease, but it is also common in healthy people.
Thyroglobulin antibodies normal range
Mayo Clinic Laboratories thyroglobulin antibody test catalog. Other assays use different cutoffs.
Hollowell et al, NHANES III (1988 to 1994), 17,353 people aged 12 and over.
Antibodies were more common in women than men and increased with age in the NHANES III data. MedlinePlus adds that pregnant women and relatives of people with autoimmune thyroiditis may also test positive.
What thyroglobulin antibodies are
Thyroglobulin is a protein made by the thyroid and used to build thyroid hormones. In autoimmune thyroid disease the immune system can make antibodies against it (TgAb) and against the enzyme thyroid peroxidase (TPO antibodies). A thyroid antibody test helps show whether thyroid symptoms or an abnormal TSH have an autoimmune cause.
What a positive TgAb means
MedlinePlus lists these conditions that can come with thyroglobulin antibodies:
- Hashimoto thyroiditis, the most common cause of an underactive thyroid
- Graves disease (an overactive thyroid)
- Subacute thyroiditis
- Other autoimmune conditions: lupus and type 1 diabetes
MedlinePlus says most people with Hashimoto disease have high levels of one or both thyroid antibodies, and the more thyroid antibodies you have, the more likely an autoimmune thyroid disorder is.
TgAb has one more use: in people treated for differentiated thyroid cancer, thyroglobulin is a tumor marker, and TgAb can make thyroglobulin read falsely low. MedlinePlus says that is why a thyroid antibody test is usually ordered alongside thyroglobulin in cancer follow-up. That monitoring belongs with your specialist, not a home kit.
TgAb vs TPO antibodies
The two antibodies overlap but do not carry the same weight. In NHANES III, TPO antibodies were significantly associated with both underactive and overactive thyroid, but TgAb were not, and TgAb alone without TPO antibodies was not significantly associated with thyroid disease (Hollowell et al, 2002). In practice that means:
| TgAb | TPOAb | Typical reading |
|---|---|---|
| Negative | Negative | No sign of thyroid autoimmunity |
| Positive | Negative | Common and often of little significance on its own; watch TSH |
| Negative | Positive | Autoimmune thyroid disease more likely; track TSH and free T4 |
| Positive | Positive | Autoimmune thyroid disease most likely, especially with an abnormal TSH |
Worked example
A 38-year-old woman with tiredness has TSH 3.8 mIU/L, free T4 in range, TPO antibodies negative and TgAb 12 IU/mL, three times Mayo's 4.0 cutoff. On the NHANES III evidence, TgAb alone is weakly linked to disease, so this pattern is usually watched rather than treated: recheck TSH in 6 to 12 months, sooner if symptoms change or she plans a pregnancy. A second woman with TSH 6.1, TPO antibodies well above her lab's cutoff and TgAb 25 IU/mL has the classic Hashimoto pattern and should see her doctor about thyroid hormone. Our hypothyroidism blood test guide explains the full workup.
Which test to use
| If you want | Test | Where |
|---|---|---|
| Both thyroid antibodies with a full thyroid panel | TSH, free T4, free T3, TPOAb, TgAb | SiPhox Thyroid Focus |
| Thyroid antibodies plus hormones, lipids and iron | Full thyroid panel and 55+ other markers | SiPhox Ultimate 360 |
| A TSH screen only | TSH | SiPhox Longevity Essentials or Heart & Metabolic |
| Thyroid cancer follow-up | Thyroglobulin with TgAb | Your specialist |
Thyroid antibodies and pregnancy
MedlinePlus says thyroid antibody testing may be needed if you are pregnant and have thyroid disease or its symptoms, because thyroid disease can harm both mother and baby, and advises getting tested as soon as you know you are pregnant. It adds that medicines to treat thyroid disease are safe in pregnancy. Positive antibodies before or during pregnancy are a reason to have TSH checked by your doctor rather than waiting for a routine test.
No special preparation is needed for a thyroid antibody test (MedlinePlus). Because cutoffs are assay-specific (Mayo uses 4.0 IU/mL, but also cites 1.8 IU/mL for interference), compare repeat results from the same lab.
At-home tests that include TgAb
Thyroglobulin antibodies are on two SiPhox panels: Thyroid Focus and Ultimate 360. Both also include TPO antibodies, TSH, free T4, free T3 and the TSH:T4 and free T3:free T4 ratios.
| SiPhox panel | Biomarkers per test | Per test, with shipping | Listed as |
|---|---|---|---|
| Thyroid Focus | 21 | $149 | Thyroglobulin antibodies (Thyroid) |
| Ultimate 360 | 62 | $274 | Thyroglobulin antibodies (Thyroid) |
SiPhox is a wellness service with no doctor review included, so bring a positive antibody result with an abnormal TSH to your doctor. See our at-home thyroid test guide.
A note on home samples: SiPhox's partner lab tests capillary blood collected from the upper arm. SiPhox says its results show a 95% to 99% correlation with venous draws in its own quarterly comparisons against Labcorp and Quest, but it has not published a study of the EasyDraw device. If a result would change a treatment decision, confirm it with a venous test through your doctor.
Thyroid Focus
A full thyroid workup including both thyroid antibodies, plus core lipids.
Check price
Ultimate 360
Everything on the four core panels plus iron studies, B12 and folate, GGT and PSA.
Check price
Frequently asked questions
What is a normal thyroglobulin antibody level?
Negative. Mayo Clinic Laboratories uses under 4.0 IU/mL as its reference value; other assays use different cutoffs.
What does a positive thyroglobulin antibody test mean?
It can go with Hashimoto thyroiditis, Graves disease or other autoimmune conditions, but about 10% of people test positive. TgAb alone, without TPO antibodies, was not linked to thyroid disease in NHANES III.
Is TgAb or TPO more important?
TPO antibodies are more closely linked to thyroid dysfunction. TgAb adds information when both are tested together.
Can thyroglobulin antibodies go away?
Levels can change over time, and after treatment for thyroid cancer they are tracked as a trend. Retest with the same lab and assay to compare.
Can I test thyroglobulin antibodies at home?
Yes. SiPhox includes TgAb on Thyroid Focus and Ultimate 360.
Sources
- MedlinePlus Medical Encyclopedia: Antithyroglobulin antibody test
- MedlinePlus Lab Tests: Thyroid antibodies
- MedlinePlus Lab Tests: Thyroglobulin
- Mayo Clinic Laboratories: Thyroglobulin antibody, serum (reference value)
- Hollowell JG et al. Serum TSH, T4 and thyroid antibodies in the United States population (NHANES III). J Clin Endocrinol Metab 2002
- SiPhox Health: panel comparison (checked 29 Sep 2026)
- SiPhox Health: Thyroid Focus panel
- SiPhox Health: Ultimate 360 panel