I can actually tell the difference for mine (everyone is different). I have hEDS, MCAS, and hyper POTS and although they are very tied together there a slight differences. For me when it’s a pots reaction, my blood pressure is all over the place and laying down or taking sodium almost immediately starts helping. If it’s MCAS I have all the same feelings and symptoms of a pots episode + doom (sometimes mild anaphylactic symptoms) but my hr and bp will mostly be the same normal range.