Thyroglobulin Test
A thyroglobulin test measures the amount of a protein called thyroglobulin in your blood. It is mainly used as a tumor marker to monitor thyroid cancer treatment and check if cancer has returned.
What this test measures
A thyroglobulin test measures the amount of a protein called thyroglobulin (Tg) in a sample of your blood. Your thyroid makes thyroglobulin along with many other important hormones.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
According to MedlinePlus, high or increasing thyroglobulin levels after treatment may mean that treatment did not remove all thyroid tissue, that you still have thyroid cancer, or that the cancer has grown or spread.
Lower-than-normal results
According to MedlinePlus, very low levels or no thyroglobulin after treatment may mean that cancer treatment successfully removed all thyroid tissue, including cancerous tissue.
Frequently asked questions
What is a thyroglobulin test?
It measures the amount of a protein called thyroglobulin in your blood. Your thyroid makes this protein.
Why is this test done?
It is mainly used as a tumor marker to monitor thyroid cancer treatment and check if cancer has returned.
Can this test diagnose thyroid cancer?
No, a thyroglobulin test alone cannot diagnose cancer. It gives information about cancer you already have.
What do high levels mean after treatment?
High or increasing levels may mean that treatment did not remove all thyroid tissue or that cancer is still present.
What do low levels mean after treatment?
Very low or undetectable levels may mean that treatment successfully removed all thyroid tissue.
Related lab tests
Sources
- MedlinePlus: Thyroglobulin — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.