Endoscopy is an very important test used in patients with suspected achlorhydria. This test can help find the cause of achlorhydria. During the procedure, after you are sedated, an endoscope which is a thin, flexible, lighted tube was passed down your throat. Then the doctor can view the lining of your esophagus, stomach, and first part of the small intestine. If abnormal areas are noted, biopsy can be obtained through the endoscope. The tissue samples will be checked by pathologist under a microscope to see what is the cause of achlorhydria.