IVIG shouldn’t affect thyroid tests,

but it mite affect some other CBC or CMP testings. [complete blood counts, complete metabolic panels]
I always try to get my labs done at a lab the day before I start my infusions. It’s had to get doctors to accept this idea tho, but I have so many doctors myself, that this way I can get a copy of the tests done for my other doctors. I always bring copies of any tests done by any other doctor to my appointment-because doc A doesn’t know what tests doc B did.
Hope this helps!