Maximum Recommended Dosage of Calcium Carbonate
The maximum recommended dosage of calcium carbonate is 2000 mg of elemental calcium per day for adults, with no more than 500 mg of elemental calcium taken at one time for optimal absorption. 1, 2
General Recommendations
- The FDA-approved labeling for calcium carbonate indicates that adults and children 12 years and older should not take more than 5 chewable tablets in a 24-hour period 2
- The safe upper limit for total calcium intake (diet plus supplements) is 2500 mg/day, but should not exceed 2000 mg/day for adults over 50 years 1
- For most adults, the recommended daily calcium intake is:
- 1000 mg for premenopausal adults (19-50 years)
- 1200 mg for postmenopausal women and men over 70 years 1
Dosing Considerations
Optimal Absorption
- Calcium carbonate should be taken with meals to ensure optimal absorption 3
- The maximum dose of elemental calcium that should be taken at one time is 500 mg to maximize absorption 3
- Calcium carbonate contains approximately 40% elemental calcium, so a 1250 mg calcium carbonate tablet provides about 500 mg of elemental calcium 4
Special Populations
- For patients with chronic kidney disease (CKD), the K/DOQI guidelines recommend that the total calcium intake from phosphate binders and diet should not exceed 2000 mg/day 5
- For dialysis patients (CKD Stage 5), calcium intake from phosphate binders should be limited to under 1500 mg/day 5
Safety Considerations
Potential Side Effects
- Common side effects of calcium supplementation include constipation, bloating, and gas 1
- Excessive calcium intake (>2000 mg/day) may increase the risk of:
Monitoring
- Persons at risk for developing milk-alkali syndrome (such as thiazide users and those with renal failure) should be monitored for alkalosis and hypercalcemia when using calcium supplements 6
- Regular monitoring of calcium levels is recommended, particularly for those on high doses 1
Important Warnings
- Do not use the maximum dosage for more than 2 weeks except under the advice and supervision of a physician 2
- Excessive intake of calcium, defined as higher than 2000 mg/day, can be potentially harmful 7
- When taking calcium carbonate as a phosphate binder in CKD, exceeding 2000 mg of elemental calcium may increase the risk of vascular calcification 5
Remember that calcium supplementation should be considered in the context of dietary calcium intake, with dietary sources being preferred over supplements whenever possible 1, 7.