Calcitonin Test
The calcitonin test measures a parafollicular C-cell peptide used chiefly as a tumour marker for medullary thyroid carcinoma and C-cell hyperplasia. Basal and calcium-stimulated concentrations help evaluate thyroid nodules, establish preoperative tumour burden, and detect persistent or recurrent disease after thyroidectomy, and they anchor surveillance in RET mutation carriers with MEN2.
2
Biomarkers
Blood (serum)
Sample
2–5 business days
Turnaround
No
Fasting
What is the Calcitonin test?
The Calcitonin Test measures the serum concentration of a parafollicular C-cell peptide whose clinical utility lies not in its weak calcium-regulating action but in its role as a sensitive tumour marker. Because C cells are the only substantial source of circulating calcitonin, the analyte scales with C-cell mass, and the question the test answers is almost always oncological: does this thyroid nodule, this family history, or this postoperative patient harbour medullary thyroid carcinoma or its precursor C-cell hyperplasia?
Within the diagnostic landscape calcitonin occupies a specialised niche quite separate from the thyroid-function panel. It does not assess thyroid hormone status and adds nothing to the TSH-led work-up of hypo- or hyperthyroidism. Instead it sits alongside RET genetic testing, carcinoembryonic antigen, and fine-needle aspiration cytology in the evaluation of nodular thyroid disease and the MEN2 syndromes. A markedly elevated basal value in the right context is strongly suggestive of MTC, modest elevations demand careful exclusion of confounders and often provocative testing, and serial measurement after surgery provides one of the most reliable means of detecting residual or recurrent disease.
What does the Calcitonin test measure?
Calcitonin is a 32-amino-acid peptide secreted by the parafollicular C cells of the thyroid, derived from the larger precursor procalcitonin by tissue-specific cleavage. Its physiological role in human calcium homeostasis is modest — it transiently opposes osteoclastic bone resorption and promotes renal calcium excretion — and healthy adults tolerate both thyroidectomy and calcitonin excess without disordered calcium levels. Its clinical value therefore rests almost entirely on its behaviour as a C-cell product rather than on its hormonal action: circulating concentrations track C-cell mass, which rises steeply in C-cell hyperplasia and medullary thyroid carcinoma.
Calcitonin is the principal biochemical marker of medullary thyroid carcinoma (MTC) and its precursor lesion, C-cell hyperplasia. Basal and stimulated concentrations are used to raise or lower suspicion of MTC in a thyroid nodule, to establish a preoperative tumour-burden baseline, and to detect persistent or recurrent disease after thyroidectomy, where a rising trend over serial measurements is more informative than any single value. It also anchors surveillance in patients with germline RET mutations and the multiple endocrine neoplasia type 2 syndromes.
Procalcitonin is the prohormone from which mature calcitonin is cleaved. Some medullary thyroid carcinomas, particularly poorly differentiated tumours, secrete procalcitonin and related peptides disproportionately to mature calcitonin, and procalcitonin is biologically more stable. It is occasionally measured to resolve discordant or borderline calcitonin results, and should not be conflated with the identically named inflammatory and sepsis biomarker, which reflects a different tissue source.
As a derived or problem-solving marker, an elevated procalcitonin alongside a disproportionately low mature calcitonin can flag dedifferentiated MTC or an assay issue affecting the calcitonin measurement. It is adjunctive and interpreted by specialists rather than used as a stand-alone screen.
Why is the Calcitonin test ordered?
- Clinicians evaluating a thyroid nodule where cytology is indeterminate or where medullary carcinoma is a differential, used as an adjunct to fine-needle aspiration
- Endocrinologists conducting biochemical surveillance in carriers of germline RET mutations and families affected by MEN2A, MEN2B, or familial medullary thyroid carcinoma
- Surgeons establishing a preoperative calcitonin baseline to gauge tumour burden and to inform the extent of neck dissection in confirmed MTC
- Oncologists and endocrinologists monitoring for persistent or recurrent disease after total thyroidectomy, interpreting the postoperative trend over serial draws
- Practitioners investigating unexplained secretory diarrhoea or flushing where a calcitonin-secreting tumour is considered
- Clinicians working up a patient with a confirmed MTC to estimate doubling time, where paired calcitonin and CEA kinetics guide prognosis
- Specialists resolving a borderline or discordant basal result who are considering calcium- or pentagastrin-stimulated provocative testing
- Multidisciplinary teams screening relatives of an index MTC case before germline genotyping results are available
Sample collection and turnaround
Sample type
Blood (serum)
Fasting required
No
Collection method
Venipuncture at patient service centre
Turnaround
2–5 business days
Collection notes
Phlebotomy at a Quest patient service centre. No fasting is required for the basal assay. Calcitonin is labile, so prompt processing and chilled handling improve reliability; where stimulated testing (for example a calcium infusion protocol) is planned, this is arranged and supervised in a clinical setting, not at a routine draw station.
Specimen requirements
Serum, drawn and separated promptly and kept chilled or frozen per the laboratory's handling protocol to limit degradation. Record the performing laboratory and assay platform, since basal cut-offs and absolute values are method-specific and serial comparison requires a consistent assay.
What can affect Calcitonin results?
Men have a larger parafollicular C-cell population than women and consequently higher basal calcitonin, which is why reference limits are partitioned by sex; applying a single cut-off risks over-calling in men and under-calling in women.
Calcitonin and its precursors are cleared in part by the kidney, so reduced glomerular filtration raises circulating concentrations independently of any C-cell pathology and is a common cause of a mildly elevated basal value.
Two-site immunometric assays are vulnerable to interference from heterophile antibodies, human anti-mouse antibodies, and rheumatoid factor, which can produce spuriously high or occasionally low results; a value discordant with the clinical picture warrants re-assay, dilution, or a different platform.
Gastrin is a physiological secretagogue for C cells, so chronic hypergastrinaemia — including that induced by prolonged proton pump inhibitor use — can modestly raise calcitonin and confound interpretation of a borderline result.
Neuroendocrine tumours (including some lung and pancreatic tumours), autoimmune thyroiditis, acute illness, and smoking can all raise calcitonin, so an elevation is not specific to medullary carcinoma and must be interpreted in context.
Calcitonin is labile; delayed separation, inadequate chilling, or freeze–thaw cycles can lower measured concentrations, while a very high tumour burden can rarely cause a high-dose hook effect that falsely lowers the reported value unless the sample is diluted.
What do Calcitonin results mean?
Elevated
A markedly raised basal calcitonin — commonly quoted thresholds above roughly 100 pg/mL — is highly suggestive of medullary thyroid carcinoma and correlates broadly with tumour burden and nodal involvement. Intermediate elevations are less specific and require exclusion of renal impairment, hypergastrinaemia, neuroendocrine tumours, and assay interference, often followed by calcium-stimulated testing. Preoperative concentration helps predict the extent of disease, and very high values raise the likelihood of distant metastasis.
Normal
A basal value within the sex-specific reference interval is reassuring in most settings but should be read against pretest probability — in a RET mutation carrier or a patient with a suspicious nodule, a normal basal result may still prompt stimulated testing, whereas in the general population it effectively argues against MTC.
Reduced
A low or undetectable basal calcitonin is the expected finding in health and carries a strong negative predictive value for clinically significant medullary carcinoma. It does not entirely exclude very early C-cell disease in a high-risk RET carrier, where provocative testing or genotype-directed surveillance may still be warranted.
Note: Results are not interchangeable between assay platforms, and serial monitoring should stay on one method and one laboratory. Sex-specific cut-offs are essential. A single modest elevation rarely establishes a diagnosis; confirmation rests on repeat testing, provocative stimulation where indicated, cytology, and histology. Calcitonin complements but does not replace RET genetic testing in the hereditary setting, and discordance between calcitonin and CEA trends can signal tumour dedifferentiation.
Frequently asked questions
It measures the serum concentration of calcitonin, a peptide made by the thyroid's parafollicular C cells. Although calcitonin plays only a minor role in calcium balance, its level tracks C-cell mass, which makes it a sensitive marker for medullary thyroid carcinoma and C-cell hyperplasia.
How to access the Calcitonin test
The Calcitonin reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.
Create Free AccountAbout this page
Published: October 7, 2026
Last reviewed: October 7, 2026
- Wells SA Jr, et al. Revised American Thyroid Association guidelines for the management of medullary thyroid carcinoma. Thyroid. (2015)
- Costante G, et al. Predictive value of serum calcitonin levels for preoperative diagnosis of medullary thyroid carcinoma in a cohort of patients with thyroid nodules. J Clin Endocrinol Metab. (2007)
- Elisei R. Routine serum calcitonin measurement in the evaluation of thyroid nodules. Best Pract Res Clin Endocrinol Metab. (2008)
- Wells SA Jr, et al. Multiple endocrine neoplasia type 2 and familial medullary thyroid carcinoma: an update. J Clin Endocrinol Metab. (2013)
- Trimboli P, et al. Calcitonin measurement in aspiration needle washout fluids and serum: diagnostic performance (verify citation/PMID). (2018)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.
Related tests
thyroid endocrine
Complete Thyroid Panel
The Complete Thyroid Panel measures six biomarkers — TSH, Free T3, Free T4, Reverse T3, TPO Antibodies, and TG Antibodies — providing the most comprehensive single-draw assessment of thyroid function, hormone conversion adequacy, and autoimmune thyroid disease status available to practitioners.
thyroid endocrine
TSH
The TSH test measures Thyroid Stimulating Hormone produced by the anterior pituitary gland. It is the recommended first-line screening test for thyroid dysfunction, with elevated TSH indicating primary hypothyroidism and suppressed TSH indicating hyperthyroidism. TSH alone does not assess T4-to-T3 conversion or exclude central hypothyroidism.
metabolic diabetes
CMP
The Comprehensive Metabolic Panel is a 14-analyte serum chemistry panel simultaneously evaluating renal function (creatinine, BUN, eGFR), hepatic function (ALT, AST, total bilirubin, albumin, total protein), metabolic status (glucose, calcium), and electrolyte-acid-base homeostasis (sodium, potassium, chloride, bicarbonate) from a single fasting serum specimen.