If you're not getting enough calcium from food alone, your doctor might recommend a supplement.
Calcium supplements come in two main forms:
Calcium carbonate
Calcium citrate
Calcium carbonate is also commonly found in over-the-counter antacids, such as Rolaids and Tums.
You need to take calcium carbonate with food, because it's easier for your body to absorb it that way. You can take calcium citrate on an empty stomach or with food.