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What is thyroglobulin test? 

Thyroglobulin test measures the amount of thyroglobulin, a protein prepared by the thyroid (a butterfly-shaped gland located in the throat) cells in blood. This test is generally used as a tumour marker test. Tumour markers or cancer markers are substances produced by healthy cells or tumour cells (cancer-causing cells) in the body in response to cancer.

In rare cases, thyroglobulin test is performed to help diagnose thyroid conditions such as hyperthyroidism (overactivity of thyroid gland that causes increased metabolic rate and rapid heartbeat) and hypothyroidism (an underactive thyroid gland that can cause retardation of mental and physical growth in adults and children).

TGB, thyroglobulin tumour marker and tg are alternative names for thyroglobulin test.

  1. Why is thyroglobulin test performed?
  2. How do you prepare for thyroglobulin test?
  3. How is thyroglobulin test performed?
  4. What do thyroglobulin test results mean?

After treating thyroid cancer using radioiodine therapy (a therapy that destroys thyroid cancer cells) little or no thyroglobulin should be present in the body. Thyroglobulin test is ordered every few months or weeks, starting shortly after the end of thyroid cancer treatment to assess the effectiveness of the treatment. It also helps monitor ongoing treatment and aids in confirming the presence or absence of thyroid cancer cells in the body after undergoing cancer treatment. 

For further diagnosis, other thyroid tests might be ordered along with thyroglobulin test.

No special preparations are required for thyroglobulin test. Your healthcare provider might recommend you not to take any vitamin B7 supplements, multivitamins or other dietary supplements at least 12 hours before the test as they might alter the test results.

A blood sample is taken from a vein in your arm after swabbing the concerned area with an antiseptic solution. The sample is collected in a vial or test tube. The whole process takes less than 5 minutes.

No serious risks are associated with this test. However, some people may experience lightheadedness after withdrawing blood and get a bruise or mild pain at the site of the injection. However, most of these symptoms are resolved quickly.

Normal results:

Low levels or absence of thyroglobulin in the blood sample indicates that cancer treatment was effective in eliminating all thyroid cancer cells from the body.

Abnormal results:

Increase in thyroglobulin levels after the successful completion of treatment indicates relapse of cancer.

High thyroglobulin or increased thyroglobulin levels indicate the possibility of cancer spreading in the body or growth of thyroid cancer cells.

A constant increase in thyroglobulin levels indicates the need for additional radioiodine therapy to eradicate the residual cancer cells in body.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor. 

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  1. American Cancer Society [internet]. Atlanta (GA), USA; Tests for Thyroid Cancer
  2. National Institute of Diabetes and Digestive and Kidney Diseases [internet]: US Department of Health and Human Services; Hashimoto's Disease
  3. American Thyroid Association. Falls Church, Virginia; THYROID CANCER
  4. American Society of Clinical Oncology [internet]; Thyroid Cancer: Diagnosis
  5. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests
  6. University of Texas: MD Anderson Cancer Center [internet]; THYROID CANCER
  7. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2018. Diagnosis of Cancer
  8. National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Tumor Markers
  9. National Institute of Diabetes and Digestive and Kidney Diseases [internet]: US Department of Health and Human Services; Graves' Disease
  10. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Thyroid Cancer: Tests After Diagnosis
  11. Clarke, William. Contemporary Practice in Clinical Chemistry. 2nd Ed, AACC Press, 2011. Pp. 501-502.
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