Cytomel (generic: liothyronine)  is a prescription medication used to treat underactive thyroid (hypothyroidism), goiters, and to test for hyperthyroidism (a condition where the thyroid gland produces too much thyroid hormone). It is a synthetic hormone used to replace hormone normally produced by the thyroid to regulate energy and metabolism.

This medication comes in tablet form to be taken once daily. Cytomel can be taken with or without food. 

Common side effects of Cytomel include nausea, diarrhea, and headache.