Hi. Thanks for your query. Noted the history of being on 50 micro-grams of Levothyroxine, was admitted in hospital for vomiting and diarrhea 2 weeks ago, was okay when left hospital but diarrhea started again on starting Levothyroxine, loosing weight, numbers are good for thyroid and has been to many Doctors. Wants to know what to do... With the history you have provided, it is sure that it is Levothyroxine with its direct actions on the gastrointestinal tract that it is causing diarrhea and hence I would advise you hte following: Reduce the dose of Levothyroxine to half that is 25 mcg and see the results under the guidance of your Doctors; repeat the thyroid function tests after 7 days to see whether the functions are within normal range or not. If withing normal range, your diarrhea problem may solve or the else you may have to shift on another medicines if you really require the thyroid supplements.