You’re trying to relieve GI issues, not create new ones, but taking certain antacids can lead to constipation, especially if you’re taking them around the clock or using more than the recommended amount.  Antacids containing calcium carbonate, like TUMS, Pepto Bismol, and some proton pump inhibitors, can cause constipation. “Occasionally, you will see a patient get diarrhea from the medication,” Dr. Tompson says. He’s found that some patients can also experience relief from constipation they are experiencing after taking these medications, but that relief should not sway patients toward taking antacids.  Talk to your doctor if you think your antacid is making it more difficult for you to have regular bowel movements.