Quick answer
Calcium citrate generally absorbs better than calcium carbonate, especially on an empty stomach, and is gentler on digestion. However, calcium carbonate contains more elemental calcium per pill, making it a cost-effective choice for those who tolerate it well.
Why absorption differences matter
Calcium absorption depends on stomach acid levels and the form of calcium. Calcium carbonate requires stomach acid to dissolve, so it is best taken with food. Calcium citrate does not rely on stomach acid, making it a better option for people with low stomach acid, such as older adults or those taking acid-reducing medications.
Stomach tolerance and side effects
Calcium carbonate can cause gas, bloating, or constipation in some people. Calcium citrate is often better tolerated because it is absorbed without needing as much stomach acid. If you have a sensitive stomach, calcium citrate is usually the gentler choice.
Calcium citrate vs calcium carbonate: trade-offs
- Absorption without food: Calcium citrate absorbs well with or without food. Calcium carbonate requires food for optimal absorption.
- Elemental calcium per dose: Calcium carbonate provides more elemental calcium per pill (typically 500-600 mg vs 200-300 mg for citrate). You may need fewer pills with carbonate.
- Stomach sensitivity: Calcium citrate is gentler and less likely to cause gas or constipation. Calcium carbonate can cause digestive discomfort in some people. If you have a sensitive stomach, choose calcium citrate.
Product facts
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Calcium Citrate: Gentle on stomach; 300 mg Calcium Citrate; NSF Gluten-Free Certified; Vegan; Supports Bone Health, Bone Density, Muscle & Nerve function. This form is ideal if you need a supplement that works on an empty stomach and is easy on digestion.
Calcium Citrate
Which one is right for you?
Best for
- People who need a gentle supplement that can be taken on an empty stomach
- Older adults or those with low stomach acid
- Vegans and those seeking a gluten-free option
Not ideal for
- Those looking for the highest calcium dose per pill at the lowest cost