Welcome to HCM. I have gone through your question and understand your concerns.
Gaining weight while on treatment with carbimazole is a good sign. It mens your hyperthyroidism
is improving. There will be significant weight loss
when you have hyperthyroidism. That lost weight is regained while on treatment with carbimazole. So no need to worry.
Kindly share with us your recent thyroid function tests
, so that we can make a better opinion
Hope I have answered your query. If you have any further questions I will be happy to help
With warm regards,
Dr Ajish TP (MD,DM)