Calcium Carbonate Dosing Recommendations
The recommended dosage of calcium carbonate should be based on elemental calcium needs, with 1000 mg/day for adults aged 19-50 years and men 51-70 years, and 1200 mg/day for women over 50 and men over 70 years, with doses greater than 500 mg taken in divided doses to improve absorption. 1, 2
Calcium Requirements by Population
- Adults aged 19-50 years and men aged 51-70 years should consume 1000 mg of elemental calcium daily 1, 2
- Women over 50 years and men over 70 years require 1200 mg of elemental calcium daily 1, 2
- The upper intake level is 2500 mg/day for people under 50 years and 2000 mg/day for those over 50 years 1, 2
- Pregnant and lactating women should follow the same recommendations as non-pregnant women in their age group 2
Calcium Carbonate Formulation
- Calcium carbonate contains 40% elemental calcium by weight, making it the most concentrated form of calcium supplement 1, 2
- A 750 mg calcium carbonate tablet provides 300 mg of elemental calcium 3
- Calcium carbonate is more cost-effective than other calcium formulations but should be taken with meals to ensure optimal absorption 1, 4
- Calcium citrate contains only 21% elemental calcium, requiring larger or more frequent doses to achieve the same elemental calcium intake 1, 2
Dosing Recommendations
- Daily calcium intake should come primarily from dietary sources when possible 1
- Supplement only the difference between dietary intake and recommended daily allowance 1
- Take no more than 500 mg of elemental calcium at one time to maximize absorption 1, 2, 4
- Divide doses greater than 500 mg of elemental calcium throughout the day 1, 2
- Take calcium carbonate with meals to optimize absorption due to the need for gastric acidity 1, 4
Special Clinical Situations
- For hypoparathyroidism: 1-2 g of elemental calcium (as calcium carbonate) three times daily 2
- For prevention of preeclampsia in pregnant women with low calcium intake: 1.5-2.0 g of elemental calcium daily 1, 2
- For patients on acid-reducing medications: calcium carbonate should still be taken with meals to improve absorption 5
- For patients with chronic kidney disease: individualized dosing based on serum calcium, phosphate, and PTH levels 2, 6
Potential Side Effects and Precautions
- Common side effects include constipation, bloating, and gastrointestinal discomfort 1
- Risk of nephrolithiasis with calcium supplements (but not with dietary calcium) 1
- Some studies suggest a potential increased cardiovascular risk with calcium supplements, though evidence is inconsistent and inconclusive 1
- Avoid taking calcium supplements with foods high in oxalate or phytate, which can decrease absorption 2
Practical Considerations
- Calcium carbonate is the most widely available and economical form of calcium supplement 1, 4
- For a person requiring 1000 mg of elemental calcium daily with a dietary intake of 500 mg, supplementation with 500 mg elemental calcium (1250 mg calcium carbonate) would be appropriate 1, 7
- For those requiring 1200 mg with a dietary intake of 600 mg, supplementation with 600 mg elemental calcium (1500 mg calcium carbonate) would be needed 1
- If higher doses are required, divide into 2-3 doses throughout the day to improve absorption and minimize side effects 1, 2