Hello. I ve had heartburn for the past two days and have been taking Zantac for it. Today it is slightly worse and accompanied by intermittnat belching that has lasted for several hours as well as mild nausea. I just used the restroom and had some stool that was very dark/black in color. I realize black stool is a sign of a GI bleed, but I m also aware that certain antacids lead to dark stool. Is the ranatadine a likely cause of the black stool, or is an ulcer more likely? If an ulcer is likely and I have recently been prescribed prilosec, and am taking ranatadine, is it absolutely necessary to go to a physician, or can it wait for a few days to see if it resolves?