Calcitonin Test

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. Follow any specific instructions from your provider.

blood draw from a vein in your arm

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

Your calcitonin results are reported as a number (level) in a blood sample. The meaning depends on why you were tested. Normal ranges and reference intervals vary by laboratory; your provider will explain what your level means for you.

• Normal calcitonin level (when tested for diagnosis or screening): A normal calcitonin level may mean that you don't have either condition, but it doesn't rule them out. Limitation: A normal calcitonin level does not rule out medullary thyroid cancer or C-cell hyperplasia, because these conditions do not always cause high calcitonin. Next step: Your provider may order other tests to learn more.
• High calcitonin level (when tested for 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: A high calcitonin level can be caused by conditions other than medullary thyroid cancer or C-cell hyperplasia, such as certain other cancers, medicines, or pregnancy. Next step: Your provider will consider other information, including other test results, to make a diagnosis.
• Low calcitonin level (when tested for diagnosis or screening): A low calcitonin level is not known to be a medical problem. Limitation: A low calcitonin level is not known to be a medical problem. Next step: No further action needed based on low calcitonin alone.
• Decreasing calcitonin level (when monitoring treatment): Calcitonin levels that decrease and stay low over time usually mean that your treatment is helping. Limitation: If the level decreases but stays higher than normal, it may mean some cancer tissue remains. Next step: If the level decreases but stays higher than normal, you may still have some cancer tissue; your provider may recommend 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

Your provider will interpret your calcitonin levels in the context of your symptoms, medical history, and other test results. If you are being monitored for medullary thyroid cancer, changes in calcitonin over time guide treatment decisions. A calcitonin stimulation test (with IV medicine) may be ordered for more accuracy.

• 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

U.S. National Library of Medicine: Calcitonin Test