Thyroxine dose really varies from patient to patient, so if you don't know exactly how much you take, having your Rx from your home country will help a Japanese doctor prescribing the right dose. Kyoto Uni hospital is a good one to go.
Thank you , good advice! I have just been to KUH
and with help of a our lovely Japanese host
at B&B Juno , navigated the system, ended up having a blood test and now have right meds again!