Constipation, gas, and burping may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. If your doctor has directed you to use this medication, remember that your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: loss of appetite, nausea/vomiting, unusual weight loss, bone/muscle pain, mental/mood changes (such as confusion), headache, increased thirst/urination, unusual weakness/tiredness, signs of kidney problems (such as change in the amount of urine). A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Some products that may interact with this drug include: digoxin, certain phosphate binders (such as calcium acetate), phosphate supplements (such as potassium phosphate), sodium polystyrene sulfonate. Calcium carbonate can decrease the absorption of other drugs. Some examples of affected drugs include tetracycline antibiotics (such as doxycycline, minocycline), bisphosphonates (such as alendronate), estramustine, iron, levothyroxine, pazopanib, strontium, quinolone antibiotics (such as ciprofloxacin, levofloxacin), among others. Separate your doses of these medications as far as possible from your doses of calcium carbonate. Ask your doctor or pharmacist about how long you should wait between doses and for help finding a dosing schedule that will work with all your medications. Check the labels on all your prescription and nonprescription/herbal products (such as supplements, vitamins) because they may contain calcium. Ask your pharmacist about using those products safely.