An over-the-counter (OTC) antacid is often used to relieve mild cases of heartburn or acid reflux. Though they are available without a doctor’s prescription, they should be taken only under a doctor’s advice.

As per the American Academy of Family Physicians -

• Different types of antacids work in different ways.
• To manage an ulcer, an antacid may need to be taken in conjunction with an antibiotic.
• If one needs more calcium to help strengthen bones, prefer an antacid that contains calcium carbonate.
• Antacids may have minor side effects in some, such as nausea, headache, diarrhea or constipation.
• Read the label carefully to make sure that you are not allergic to any of the ingredients.
• People with kidney disease may not be able to take all types of antacids.
• An antacid may interact with other medications.

So, talk to the doctor before taking an antacid.