I get muscle jerks sometimes, particularly in my arms/hands, when I'm severely dehydrated. Sometimes in my flares I just can't get enough fluids to absorb into my system and I have to go get IV fluids, so please consider doing that if this continues. One test of dehydration is to pinch the skin on the back of your hand. If it snaps right back in less than a second, you're probably okay, but if it takes a second or longer to go back, then you're dehydrated.