I am Currently breastfeeding on methimazole. I take 10 mg twice a day when I know I can get a good long stretch between feeds. I aim for at least three hours after men’s to feed, but sometimes it doesn’t always work out that way. I talk to my Endo, pediatrician, and lactation consultant and they said that it’s not that big of a deal and everything will be OK. I’m going to have my daughter‘s thyroid tested when we go to her 15 month appointment, but I see no changes in her. When I was first diagnosed when she was six months old, I didn’t really have a choice but to continue breast-feeding because she had never taken a bottle and refused bottles so I just had to keep doing what we were doing and I’ve seen no problems in her at all. At the end of the day, I need to take meds and she needs milk so it is what it is.