I recently received a question about gluten in communion wafers. The short answer is that unless great care has been taken by the clergy to select a wafer that is gluten free, you must assume that it is a normal, wheat-based wafer and will contain the toxin we call gluten. Some studies have shown that even a communion wafer-sized piece of bread once a month is enough to keep some gluten sensitive people in a high risk category for early death. Also studies have indicated that the autoimmune windup resulting from a small quantity of bread like a communion wafer can persist for six months in some cases.
For a gluten sensitive person, being exposed to gluten once in a while in even small doses is not trivial. This is why we talk of the gluten free diet instead of the low gluten diet. The amount of reaction that you might experience will depend on your particular makeup. Some people will experience some brain fog, intestinal upset and maybe headaches and/or joint pain, for example. I hesitate to mention any of these possible symptoms because if you don't experience any of these you may incorrectly assume that no damage is being done. The list of complications to gluten is very long and many of these like osteoporosis will show no noticeable symptoms even though the consequences are severe.
Most Christian groups have decided that it is better to serve grape juice rather than the traditional wine as a helpful gesture to those who don't do well with even trace amounts of alcohol. In like fashion it also makes sense to make the necessary changes to help the 20+ million Americans who are slowly discovering their unforgiving gluten intolerance.
A few groups have decided that unless the wafer contains gluten, it can't be considered genuine for sacrament purposes. I did spend some time in formal religious training so will weigh in on the idea of the elements of communion. The Last Supper was shared by Jesus and a small number of followers. The wine and bread were most probably not carefully selected but were simply chosen from what was very common and readily available in the markets of the day. If the setting had been another part of the world, we might be using poi and coconut milk instead of wine and bread for communion. Focusing on the wine and bread misses the much larger point of what was about to take place in the life and death of Jesus and the hope of the resurrection that was to follow.
I suggest you keep in mind the big picture here and talk with the clergy at your favorite place of worship. I would respectfully point out that for your health this a black and white issue and request that alternatives be provided. If the answer is "no", then I, personally would keep looking for a way to honor my body and faith at the same time.