Monday Pharmaceutical Mystery: January 13

Why does a patient's levothyroxine dose need to be adjusted?

Your patient, AR, presents to the pharmacy after an endocrinologist visit. “It’s so strange,” she says. “I have been on the same dose of levothyroxine for years but now my doctor is changing the dose. Nothing else has changed.”

Mystery: Why does AR’s levothyroxine dose need to be adjusted?

Solution: AR happens to mention that she has been on the Mediterranean diet for several months. She says she has been eating a lot of fruits, vegetables, fish, beans, and has been constantly snacking on walnuts to curb her hunger.

You look up drug-food interactions for levothyroxine, out of curiosity, and sure enough, the package insert states: “Consumption of certain foods may affect levothyroxine absorption thereby necessitating adjustments in dosing. Soybean flour (infant formula), cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the GI tract.”


Levothyroxine package insert Accessed December 12, 2019.