 [ Symptoms ] after every meal i get a really uncomfortable bloated feeling gasy and feeling extremely tired what may cause this  i took a pregnancy test and am not pregnant  i thought it was a lactose intolerance but have found that is not it after doing a lactose free diet [ Disease ] bun stands for blood urea nitrogen one of the values checked on a routine blood chemistry test nitrogen is excreted from the body by the kidneys and bun levels rise in people with chronic kidney disease bun may also be temporarily high in people who are dehydrated