Take Your Thyroid Hormone before Breakfast

Doctors often tell their patients to take thyroid hormone medication on an empty stomach, before breakfast. But there’s been no evidence to support this advice, and it’s quickly forgotten during the subsequent months and years after the first prescription. Now a study has been reported at the Endocrine Society meeting that emphasizes the need for consistency with the dictum “in a fasting state”.

Investigators studied 65 patients who were taking levothyroxine for hypothyroidism or thyroid cancer. The patients were asked to vary their dosing of the medication for 3 8-week periods:

After an overnight fast, at least 1 hour before breakfast

At bedtime, at least 2 hours after the evening meal

Within 20 minutes of finishing breakfast

Serum TSH (thyroid-stimulating hormone) concentration was measured at baseline and at the end of each 8-week period. The average level with the fasting-state patients was 1.06 mIU/L; when the medication was taken with breakfast it was 2.93 mIU/L, and when taken at bedtime 2.19 mIU/L.

The ideal range of values for TSH is between 0.3 and 3.0 mIU/L, so that it’s clear that taking your hormone medication fasting is a preferred way. Obviously, some of the with-breakfast and at-bedtime patients would have been over the upper limit of 3.0 mIU/L at times.

I checked my wife’s levothyroxine bottle. Nothing on it about “take on an empty stomach” or “take when fasting”. Luckily she’s still taking hers before breakfast, based on her doctor’s instructions 8 years ago. But other may not be aware of this stricture, or have forgotten it. So, if the cap fits, . . .