Thyroid
Thyroglobulin antibodies blood test
A thyroglobulin antibodies (anti-Tg) blood test looks for antibodies your immune system can make against your own thyroid. A positive result points to autoimmune thyroid disease, the most common underlying cause of an under- or over-active thyroid, and it's usually interpreted alongside anti-TPO antibodies and your thyroid function.
- What it measures
- Thyroid autoantibodies (anti-Tg, tested with anti-TPO)
- Sample
- Venous blood sample
- Fasting
- Not required
- Also known as
- anti-Tg, anti-thyroglobulin antibodies, thyroid antibodies
- Included in 57 Health tests
- 3 panels, from £60
What does a high thyroglobulin antibody level mean?
A positive or raised thyroglobulin antibody result indicates thyroid autoimmunity: your immune system is producing antibodies against the thyroid. This is common in Hashimoto's thyroiditis (a frequent cause of an underactive thyroid) and can also occur in Graves' disease.
Antibodies can be present before thyroid function changes, so a positive result with normal TSH may mean a higher future risk rather than a current problem. It's interpreted alongside anti-TPO, TSH and free T4.
What does a low thyroglobulin antibody level mean?
A negative (or low) result means these thyroid antibodies weren't detected, which makes autoimmune thyroid disease less likely as a cause of your symptoms.
It doesn't rule out every thyroid problem, so it's read alongside your thyroid function tests (TSH and free T4).
When to consider a thyroglobulin antibody test
- An abnormal or borderline TSH
- Symptoms of an under- or over-active thyroid
- A family history of thyroid or autoimmune disease
- Planning or during pregnancy with thyroid concerns
- Clarifying whether a thyroid problem is autoimmune
Frequently asked questions
This page is general information about a blood marker and is not medical advice or a diagnosis. A thyroglobulin antibody test screens and gives context; results are interpreted by a clinician alongside your symptoms, history and other markers. Always follow the guidance on your own report.