What workup do you recommend for patients requiring higher-than-expected levothyroxine doses for their weight?

If someone is on a significantly greater than expected dose of levothyroxine for their weight, I take a careful history to confirm they are taking the medication appropriately. Usually, the issue is mistiming of medication with regards to proximity to food or supplements - or even simple nonadherenc...

I start off with making sure they are compliant, by calling the pharmacy and looking to see if refills are on time, and also see if they are taking it properly and away from medications or food that will impair absorption.

Rarely, I have found a few appropriately chosen patients that "normalized" doses of standard preparations of LT4 by adding Lactaid.

Always repeat a TFT with a TPO ab since many TSH will normalize. If it continues with high TSH and normal Free T4, I would consider Levothryoxine if:

1. Convincing hypothyroid symptoms,
2. Positive TPO antibodies (Tg antibodies are not predictive of hypothyroidism),
3. Planned pregnancy or TSH > 10 despite ...