FMLA

I'm not sure if this has been posted before, but I just spoke to my aunt who recently retired as head of HR for a major fortune 500 company. She informed me that any leave taken for celiac (or any other condition covered under the ADA) MUST be taken as FMLA leave. And you have to specifically tell your company you want the leave counted towards your FMLA leave.

You cannot take a regular sick day for a gluten reaction and still be covered under the ADA for it.

tl;dr: To not be fired for taking leave because of celiac, it must be taken as FMLA leave.

disclaimer: obviously this is for the US only.