This is a clinical practice guideline for individuals with or suspected of having Medullary thyroid carcinoma (MTC). The guideline provides recommendations on diagnosis, surgical treatment, and follow-up care. The use of chemotherapy and/or radiotherapy in the management of individuals with metastatic MTC is also discussed. The appropriate use of RET proto-oncogene molecular testing during diagnostic assessment is discussed, and the potential value in the use of tyrosine-kinase inhibitors as a treatment option is reviewed. Outcomes of interest include survival rate (median, overall, 10-year, progression-free), sensitivity and specificity of diagnostic tests, cure rate, rate of remission, and recurrence rate.