It's good that you've seen your doctor and been checked for some of the most common causes of excessive thirst -- diabetes, kidney and/or liver-related disorders, etc. However, in researching I'm not finding it to be listed as a symptom of acid reflux, so I'm not sure as to the reasoning of being prescribed Zantac. What I do find are other possible causes for excessive thirst, ranging from simple to complex:   -- Recently eating salty or spicy foods   --  Excessive loss of water and salt, possibly caused by not drinking enough water (dehydration), fluid loss during exercise, or experiencing profuse sweating, vomiting or diarrhea   -- Drugs such as anticholinergics, demeclocycline, diuretics, phenothiazines   -- An underlying disease (physical or emotional)     I hope this information is helpful. If this continues for you, be sure to keep your doctor involved.   Best regards, Maria