Can an upper endoscopy tell a doctor if a person is having problems with heartburn and stomach acid?

Yes: By revealing esophageal inflammation. Some other tests may be used, too, checking the pH in the distal esophagus and so on. Usually heartburn symptoms with esophageal inflammation revealed by upper endoscopy will suffice in making the diagnosis.

Yes: Endoscopy of the esophagus is a procedure using a tiny camera on a flexible tube to examine the upper GI tract. Acid reflux can cause changes to the lining of the stomach and esophagus which are often visible to the camera. Your doctor may also take a biopsy of the areas in question during the procedure.