Calcitonin tests measure the level of calcitonin, a hormone produced mainly by the thyroid’s parafollicular (C) cells, in the blood. Because medullary thyroid carcinoma (MTC) arises from C cells and commonly secretes calcitonin, an elevated blood calcitonin is used as a tumor marker to help detect MTC, assess risk in people with thyroid nodules or hereditary MEN2 syndromes, and monitor for residual disease or recurrence after treatment.

Interpretation requires caution: markedly high calcitonin strongly suggests C‑cell disease like MTC, but mild elevations can occur with other conditions (renal failure, other neuroendocrine tumors, smoking, certain drugs), and stimulation tests or serial measurements are sometimes used to clarify uncertain results. Clinical context and further diagnostic workup are essential.

Calcitonin is measured from a venous blood sample: a phlebotomist draws blood from a vein (usually in the arm) into the appropriate collection tube and the sample is sent to the laboratory for analysis.

Some labs ask that the blood be taken in the morning and may recommend fasting or avoiding smoking and heavy exercise beforehand; if a basal result is borderline, a clinician may request a supervised stimulation test (e.g., calcium or pentagastrin challenge) that requires specialized monitoring. Always follow the specific instructions given by your testing provider or laboratory.

Calcitonin is a hormone produced by the thyroid’s C‑cells; a low or normal calcitonin makes medullary thyroid carcinoma (MTC) unlikely, while a clearly elevated result suggests increased C‑cell activity and raises concern for MTC or C‑cell hyperplasia. The amount of elevation often relates to tumor burden, but interpretation depends on the laboratory’s reference range, the specific assay used, and whether the elevation is persistent.

Calcitonin can also be raised by non‑cancer causes (e.g., some chronic illnesses, smoking, certain medications and laboratory variability), so mild or isolated increases are often rechecked before concluding there is cancer. Clinicians commonly repeat the same test, may use a calcitonin stimulation test or imaging, and consider genetic testing (RET) when MTC is suspected to determine your actual cancer risk; rely on your lab’s reference range and specialist interpretation to understand what your personal result means.

Calcitonin is a sensitive tumor marker for medullary thyroid carcinoma (MTC) and is particularly useful for detecting and monitoring established disease, but it is not perfectly specific or standardized. Elevated calcitonin strongly suggests C‑cell pathology (C‑cell hyperplasia or MTC), yet false positives can occur with other conditions (renal failure, other neuroendocrine tumors), certain drugs, and smoking; false negatives are possible with very small or early tumors and with assay variability. Laboratory methods and cutoffs differ between assays and between men and women, so absolute values must be interpreted in context.

Because of these limitations, calcitonin testing is most reliable when used alongside clinical evaluation, imaging, and—when needed—stimulation testing (historically pentagastrin or intravenous calcium) to improve sensitivity. It’s widely accepted for postoperative surveillance and detecting recurrence of MTC, while routine universal screening of all thyroid nodules with calcitonin remains controversial and depends on local guidelines, assay quality, and how results will change management.

How often you should test calcitonin depends on why it’s being measured: for screening of thyroid nodules or at‑risk people, for diagnosis, or for monitoring known medullary thyroid carcinoma (MTC) or RET mutation carriers. Routine screening is not universally required, but a baseline calcitonin is often obtained when evaluating a thyroid nodule; repeat testing is usually done only if the baseline is elevated or the nodule or clinical picture changes.

For monitoring after treatment of MTC, most specialists check calcitonin (and CEA) more frequently initially — commonly every 3–6 months in the first year after surgery — then every 6–12 months for several years, and often yearly long‑term because recurrence can occur late. RET mutation carriers and others at high risk typically follow a regular schedule (often annually or as recommended by a specialist) beginning at the age indicated by their mutation risk. Follow the schedule your endocrinologist or cancer team recommends, since timing is individualized by disease status, risk, and other test results.

No — Calcitonin test results highlight patterns of imbalance or resilience, not a standalone medical diagnosis; they can indicate a signal that warrants further evaluation but do not by themselves confirm or rule out cancer.

They should be interpreted alongside symptoms, medical history, imaging and other lab or biomarker data by a qualified clinician, who will integrate all information to determine whether additional diagnostic testing or specialist referral is needed.

Calcitonin is a tumor marker produced by thyroid C‑cells; elevated results are a signal, not a self‑treatable problem. There is no reliable “home” method to lower calcitonin — management depends on the underlying cause (for example, medullary thyroid carcinoma (MTC) requires surgical and specialist care), so the first step is diagnostic follow‑up rather than trying to change the number yourself.

Practical next steps are: arrange prompt evaluation by an endocrinologist, repeat the blood test (same lab and assay if possible) to confirm the result, and proceed with recommended workup (neck ultrasound, possible stimulation testing or genetic testing for RET mutations if MTC is suspected). If a non‑thyroid cause is identified (e.g., smoking, chronic kidney disease, or other conditions), treating those causes and stopping smoking can reduce spuriously elevated levels; if MTC is diagnosed the definitive intervention is surgical and guided by specialists.

Do not delay specialist referral — an appropriate diagnosis and treatment plan will both address cancer risk and normalize calcitonin if it is driven by a treatable condition. Follow your clinician’s recommendations and avoid unproven supplements or therapies aimed at “lowering” calcitonin without medical supervision.