Euthyrox 25 mcg is a prescription medication containing levothyroxine sodium, a synthetic thyroid hormone. It is used to treat hypothyroidism (underactive thyroid) and to suppress thyroid hormone production in patients with certain types of thyroid conditions. Each tablet contains 25 micrograms of levothyroxine sodium as the active ingredient. This medication requires a prescription and proper dosing should be determined by a healthcare provider based on individual patient needs and regular thyroid function monitoring. The dosage may need to be adjusted over time. Store at room temperature away from heat, moisture and light. This is a maintenance medication that typically needs to be taken long-term.