What special precautions should I follow?  

Before taking calcium carbonate,

• tell your doctor and pharmacist if you are allergic to calcium carbonate or any other drugs.
• tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially digoxin (Lanoxin), etidronate (Didronel), phenytoin (Dilantin), tetracycline (Sumycin), and vitamins. Do not take calcium carbonate within 1-2 hours of taking other medicines. Calcium may decrease the effectiveness of the other medicine.
• tell your doctor if you have or have ever had kidney disease or stomach conditions.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking calcium carbonate, call your doctor.

What should I do if I forget a dose?  

If you are taking calcium carbonate on a regular schedule, take the missed dose as soon you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.