Calcium Supplements: Calcium Carbonate or Calcium Citrate for Vegetarians?

Comparing the Two Main Types of Calcium Supplements

• Calcium carbonate: High in elemental calcium (about 40%) and inexpensive, but it needs stomach acid to dissolve, so it's best taken with meals. Older adults with reduced stomach acid production may absorb it less well.
• Calcium citrate: Lower in elemental calcium (about 21%), but it absorbs reasonably well without needing stomach acid, so it can be taken on an empty stomach. It's better suited to people with low stomach acid or those on long-term acid-reducing medication.

Because the two differ in elemental calcium content, taking "one tablet" of each doesn't deliver the same amount of actual calcium — check the elemental calcium amount printed on the label rather than the total tablet weight.

Details Vegetarians Should Keep in Mind

Calcium supplements should come after dietary adjustments, not instead of them — prioritize getting calcium from soy products, dark leafy greens, and fortified plant milk, and only consider a supplement if your diet genuinely falls short. Don't take too much in a single dose — the body has a limit on how much calcium it can absorb at once (generally thought to be around 500 milligrams), so splitting doses (for example, once in the morning and once in the evening) works better than one large dose at a time.

Tips for Taking Calcium Supplements

Avoid taking calcium at the same time as iron supplements, since the two compete for absorption. Pairing calcium intake with vitamin D and regular exercise gives more complete results. If you have a history of kidney stones, consult a doctor before starting a calcium supplement.