How many 600 mg calcium carbonate tablets should a 60-year-old female on anastrozole (aromatase inhibitor) take daily to meet the recommended 1200 mg calcium intake?

Calcium Carbonate Supplementation for a 60-Year-Old Female on Anastrozole

For a 60-year-old female on anastrozole, two 600 mg calcium carbonate tablets daily (providing 480 mg elemental calcium per tablet, for a total of 960 mg elemental calcium) should be taken with meals to meet the recommended 1200 mg daily calcium intake. 1, 2

Understanding Calcium Carbonate Dosing

Calcium carbonate contains 40% elemental calcium, which means:

• Each 600 mg calcium carbonate tablet provides 240 mg of elemental calcium
• To reach the recommended 1200 mg of elemental calcium daily, the patient would need:
  • Approximately 300 mg from non-dairy dietary sources 1
  • Approximately 740 mg from dairy products (one 8-oz serving of yogurt plus one glass of milk daily) 1
  • The remaining amount (approximately 160 mg) from supplements

However, since the patient is on anastrozole for breast cancer treatment, which increases bone loss risk, ensuring adequate calcium intake is particularly important:

• For optimal absorption, calcium supplements should be taken in divided doses of no more than 500-600 mg elemental calcium at once 1, 2
• Calcium carbonate should be taken with meals to ensure proper absorption, as it requires gastric acid 1, 2

Practical Supplementation Approach

Given the patient's current dietary calcium intake (approximately 1040 mg from diet) and the need to reach 1200 mg daily:

1. Morning dose: One 600 mg calcium carbonate tablet with breakfast (providing 240 mg elemental calcium)
2. Evening dose: One 600 mg calcium carbonate tablet with dinner (providing another 240 mg elemental calcium)

This approach provides approximately 1520 mg total elemental calcium daily (1040 mg from diet + 480 mg from supplements), which is above the recommended 1200 mg but well below the upper limit of 2000 mg for adults over 50 years 1, 2.

Important Considerations

• Calcium supplements should be taken with meals to optimize absorption, particularly for calcium carbonate 1, 2
• If the patient experiences gastrointestinal side effects (constipation, bloating), calcium citrate may be considered as an alternative, though it provides less elemental calcium (21% vs 40%) 1
• Vitamin D supplementation (400-600 IU daily) should be continued alongside calcium to ensure proper calcium absorption 1, 2
• Regular weight-bearing exercise should be encouraged to further mitigate bone loss risk 2
• Monitor for potential side effects of calcium supplementation, including constipation, bloating, and rarely, kidney stones 1, 3

Caution

Avoid exceeding 2000 mg of total calcium daily (the upper intake level for adults over 50), as excessive supplementation may increase the risk of kidney stones and potentially cardiovascular events 1, 2.