Thyroid Tests
Answers to common questions about thyroid tests.
Questions on this page
What blood tests are used to check the thyroid?
The most commonly used tests are:
- TSH → Free T4
- Depending on the situation, your doctor may also request:
- T3
- Anti-TPO antibodies
- Anti-thyroglobulin antibodies
- TSH receptor antibodies
The tests required depend on the clinical situation. NIDDK Reference
What does a high TSH mean?
A high TSH often suggests that the thyroid is underactive.
The result needs to be interpreted together with Free T4 and the clinical situation.
What does a low TSH mean?
A low TSH can occur when there is too much thyroid hormone in the body.
It can also occur for other reasons, so additional testing may be needed.
Can TSH be abnormal but T4 be normal?
Yes.
This may represent subclinical hypothyroidism or subclinical hyperthyroidism, depending on the TSH level and clinical context.
Do I need a thyroid test if I feel completely normal?
Not everyone needs routine thyroid testing.
Testing is more useful when symptoms, risk factors, pregnancy, medications or other clinical reasons are present.