Question: what is the difference between levothyroxine and armour thyroid?
Answer: Synthroid contains T4 (thyroxine) only, whereas Armour contains both T4 and T3 (tri-iodothyronine). T3 is more biologically active than T4. 4. Synthroid's actions may take a few hours, whereas Armour Thyroid will begin to work within an hour.