If there is remaining living thyroid tissue after RAI, it’s rare, but the tissue *can* regenerate and cause a recurrence of hyperthyroidism. However, the more common scenario is that patients find that their need for replacement hormone can change over time, so a dosage adjustment might help.
However, as gatorgirly noted, making a dosage adjustment on your own without labs can actually set you back instead of making you feel better, so I would definitely call your endo's office ASAP and ask for new labs. If your schedule is flexible, ask to be placed on their cancellation list, which can potentially get you in sooner.
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