Calcitonin Test
Reviewed
Also called: thyrocalcitonin, CT, human calcitonin, hCT
A calcitonin test uses a sample of your blood to measure your levels of calcitonin, a hormone made in your thyroid gland by cells called “C cells.”
Specimen: blood
Why this test may be ordered
- To help diagnose C-cell hyperplasia or medullary thyroid cancer in people with symptoms (lump in neck, swollen lymph nodes, throat pain, trouble swallowing, voice changes, cough, diarrhea).
- To screen people at high risk for medullary thyroid cancer, such as those with a family history of multiple endocrine neoplasia type 2 (MEN2).
- To monitor how well treatment for medullary thyroid cancer is working.
- To check whether medullary thyroid cancer has returned after treatment.
Preparation and collection
You may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if you need to fast and if there are any special instructions to follow.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
The meaning of your calcitonin test results depends on the reason you were tested.
- Normal calcitonin level (diagnosis or screening): A normal calcitonin level may mean that you don't have either condition, but it doesn't rule them out. Limitation: That's because medullary thyroid cancer and C-cell hyperplasia don't always cause high calcitonin. Next step: Your provider may order other tests to learn more.
- High calcitonin level (diagnosis or screening): A high calcitonin level means that the C cells in your thyroid are making too much calcitonin. The higher the level, the more likely it is that you have medullary thyroid cancer or C-cell hyperplasia. Limitation: However, high calcitonin levels may be caused by other conditions, including certain other cancers, certain medicines, and pregnancy. Next step: So, to make a diagnosis, your provider will consider other information, including other test results.
- Decreasing and staying low (monitoring treatment): Calcitonin levels that decrease and stay low over time usually mean that your treatment is helping. Limitation: The meaning of your test results depends on the type of treatment you're having or had. Next step: Ask your provider to explain what your test results mean for your health.
- Decreasing but still high, or increasing (monitoring treatment): A calcitonin level that increases over time usually means that your cancer has returned or spread to other parts of your body. Limitation: A calcitonin level that decreases but is still higher than normal may mean that you still have some cancer tissue left in your body. Next step: You may need more tests and treatment.
- A normal calcitonin level does not rule out medullary thyroid cancer or C-cell hyperplasia, because these conditions do not always cause high calcitonin.
- A high calcitonin level can be caused by other conditions, including certain other cancers, some medicines, and pregnancy. Therefore, a high level alone is not a diagnosis; your provider will consider other test results.
- There is no known medical problem associated with a low calcitonin level.
- For screening, the test is most useful in people with a family history of multiple endocrine neoplasia type 2 (MEN2) and may be repeated regularly.
What to do next
Ask your provider to explain what your test results mean for your health.
- What do my calcitonin results mean in my situation?
- Will I need other tests, such as a RET gene test or a calcitonin stimulation test?
- How often should I have this test if I have a family history of MEN2?
- Do I need to fast before this test?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.