Hypersensitivity to the active substance or to any of the excipients.
Untreated adrenal insufficiency, untreated pituitary insufficiency, and untreated thyrotoxicosis.
Treatment with Euthyrox must not be initiated in acute myocardial infarction, acute myocarditis, and acute pancarditis.
Combination therapy of levothyroxine and an antithyroid agent for hyperthyroidism is not indicated during pregnancy (see Use in Pregnancy & Lactation).