I have Graves and suffered with Hyperhtyroidism and was on Carbimazole which is the same medication as Methimazole.
Yes you can gain weight...I gained 16 kilograms.
It is where the MMI is blocking the thyroid thus slowing down the metabolism.
I eventually had RAI due to thyroid storm and then found out I had Thyca so a keyhole TT was done due to me having a heart problem (Full anaesetic was too dangerous).
This was June and September 2008.
I look back now and dont know how I ever made it through those early days but I feel great now and have got fulltime work and am doing an online study course too.
Divide your MMI out over 3 times a day as it stops you getting hyper spikes late in the afternoon and evening.
When Hyperthyroid, the thyroid produces hormones around 3-4am every morning. I always made sure I took my 3rd dose of med before bed or I would wake up sweating and heart racing around 4am.
Also have yr bloods checked every 3-4 weeks as you can go hypo very quickly.
Usually the starting dose for hyperthyroidism is 30mg daily.
As I said previously...divide this dose into 3 times a day and you will soon start to feel better than you do now.
Also ask your Docotr for a beta blocker to stop the heart racing. Usually Inderal is prescribed untiol the ATD's (anth-thyroid meds) kick in.
Do you know your levels and also your antibody levels?
If so, post here as many here have hyperthyroidism and Graves and can help you.
Any questions...feel free to message me.
Take Care :)
I am not familar with your meds, mostly because I am Hypo/Hashi's, but I do know that your metabolism runs at a faster pace than Hypo, and your meds should be trying to slow you down, so if you still have the same calorie intake you could put on weight, I know as a Hypo my meds increase my metabolism, I would think yours would be the opposite, but by me responding, it will bump up your post and maybe a member more experienced with your issue will answer you also. Good Luck FTB4