Levothyroxine (T4)

Levothyroxine (L-thyroxine, tradename: Synthroid), is a manufactured form of the thyroid hormone thyroxine (T4).

Be careful dosing levothyroxine

Levothyroxine should only ever be prescribed in micrograms (mcg) to reduce the risk of prescription error. Common calculation errors when converting from mcg to mg (e.g. - 0.025mg to 25mcg (correct), may sometimes be mistakenly converted to 250mcg (a 10-fold dose increase error).
  • Tachycardia, heat intolerance, tremors, arrhythmias
  • May be abused in those seeking weight loss