Hi, There seems no side effect of yellow stools, neither with Nexium, nor with tums. Still, continuous yellow stools, sometimes may be very much normal and may be due to certain diets like diets rich in sweet potatoes, carrots or foods high in yellow food coloring etc. Still, sometimes, continuous yellow stools may be due to certain medical conditions like: - Pancreas related problems, like pancreatitis, pancreatic cancer, blockage of pancreatic duct etc. - Gall bladder related problems, like gall stones, cholecystitis, blockage of common bile duct, tumors of gall bladder etc. - Liver problems like hepatitis, liver cirrhosis, liver cancer etc. - Celiac disease - Some parasitic infections like giardiasis and so many other disease Therefore, I will advise you, to consult some gastroenterologist and should be investigated for any such disorder, if present and treatment done accordingly, if required under guidance of your doctor. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Satnarain Bansal, General & Family Physician