Hello and welcome to Healthcare Magic. Thanks for your query. There is no specific research eveidence to state that taking marijuana affects the thyroid gkand. But generally, it is well known that marijuana can have a negative impact on a person s overall health. It is not advisable to take marijuana when you are on thyroid medication because there is a possibility of drug interactions. Marijuana may affect the absorption or effect of the medication. There is no clear scientific evidence that marijuana can be used in the treatment of hyperthyroidism and it is not liscenced for this particular use. Wish you all the best. Regards, Dr. Jonas Sundarakumar Consultant Psychiatrist