Calcium carbonate vs. calcium citrate: What’s the difference?

Calcium is a mineral found in many foods and supplements. Our bodies need calcium for many essential functions. Calcium can be found in foods such as dairy products, green vegetables, almonds and canned fish with bones. Calcium supplements are also available if it’s not possible to get enough from food. If you’re considering a calcium supplement, you may be wondering how calcium carbonate and calcium citrate compare.

The two most common types of calcium supplements are calcium carbonate and calcium citrate.

Calcium carbonate supplements should be taken with food for optimal absorption. Calcium carbonate contains more elemental calcium than other kinds of calcium supplements. Elemental calcium is the actual amount of calcium absorbed by the body.

Calcium citrate supplements can be taken on an empty stomach and may be more easily absorbed than other forms. Calcium citrate supplements contain less elemental calcium, so you may need to take more pills to meet your calcium needs. Even though calcium citrate can be taken on an empty stomach, it's generally a good idea to take a calcium supplement with food for the best absorption.

Other less common types of calcium supplements include calcium gluconate, calcium lactate and calcium phosphate. Calcium can also be found in other supplements, including multivitamins or in combination with vitamin D or other minerals. Work with your healthcare provider to determine if you need a calcium supplement and which one is right for you. 

Dosage amounts can depend on several factors, including your age, dietary calcium intake and the reason for taking calcium. If your healthcare provider recommends a calcium supplement, ask them how much calcium you should take.

There are many calcium supplements available. Always speak with a pharmacist or healthcare provider if you have questions about calcium supplements.

Clinically reviewed by Amy Magill, MA, RDN, October 2024.