How Is Dehydration Diagnosed?

i SUSPECT THAT MY HUSBAND AND i ARE DEHYDRATED. i AM MORE SO THAN HIM BECAUSE OF MY UNPLEASANT DRY MOUTH. hOWEVER i DRINK MORE WATER THAN HE DOES. WE JUST RETURNED FROM MEXICO AND FEEL SLUGGISH, HAVE BEEN SLEEPING FOR THE LAST FEW DAYS, no appetite. I know we have to be checked and want to know what the procedure is to detect dehydration. My urine is white and foamy, his is yellow but strongly reduced in quantity. PLUS I HAVE DIARRHEA nad have had it for over a year.