From the Guidelines
Calcium carbonate supplements should be taken in doses of 500-1000 mg, 2-3 times daily with meals, to achieve the recommended 1000-1200 mg of elemental calcium per day for most adults. When considering calcium supplementation, it's crucial to prioritize the amount of elemental calcium, as this is what the body absorbs and utilizes 1. The choice between different calcium supplements, such as calcium carbonate and calcium citrate, depends on various factors including gastrointestinal tolerance and the presence of stomach acid, which affects absorption 1.
Key Considerations for Calcium Carbonate Supplementation
- Calcium carbonate provides a high elemental calcium content (40%) and is inexpensive and widely available 1.
- It should be taken with meals to enhance absorption, as gastric acidity is required for sufficient breakdown and utilization of the calcium 1.
- Divided doses are recommended if daily supplementation exceeds 500 mg of elemental calcium to improve absorption and minimize gastrointestinal side effects such as constipation and bloating 1.
- For those who experience bothersome gastrointestinal symptoms with calcium carbonate, calcium citrate may be a reasonable alternative, although it provides less elemental calcium (21%) 1.
Practical Guidance for Patients
- Always check the product label for the amount of elemental calcium, as this varies between different calcium salts 1.
- Be aware of potential side effects such as constipation, gas, or bloating, and adjust the dose or switch to a different form of calcium if these become problematic 1.
- Consider dietary sources of calcium as the first line of intake, given their wide availability and association with few adverse effects, reserving supplements for when dietary intake is inadequate 1.
From the FDA Drug Label
Adults and children 12 years and older chew and swallow 1 to 2 chewable tablets every 2-4 hours as needed. Do not exceed 5 chewable tablets in 24 hours. Do not take more than 5 chewable tablets in a 24-hour period, or use the maximum dosage for more than 2 weeks, except under the advice and supervision of a physician. The recommended dose and frequency of calcium carbonate (CaCO3) supplementation is:
- 1 to 2 chewable tablets every 2-4 hours as needed for adults and children 12 years and older.
- Do not exceed 5 chewable tablets in 24 hours 2 2. Children under 12 years should consult a doctor 2.
From the Research
Recommended Dose and Frequency of Calcium Carbonate Supplementation
- The recommended dose of calcium carbonate supplementation is up to 2500 mg (62.5 mmol) per day, as intakes up to this amount are considered safe for virtually all patients 3.
- A divided dose regimen, such as taking calcium carbonate with meals and at bedtime (4 times a day), results in substantially greater absorption of the supplement than taking it once a day 3.
- The maximum dose of elemental calcium that should be taken at a time is 500 mg, and calcium carbonate should be taken with a meal to ensure optimal absorption 4.
- Calcium supplements should be taken with 8 ounces of water or other liquid, and patients with achlorhydria should avoid taking calcium carbonate tablets 5.
Considerations for Calcium Carbonate Supplementation
- Patients exhibit a wide range of absorption efficiencies, and it is desirable to assess absorption fraction before beginning a supplement regimen 3.
- Calcium carbonate preparations are absorbed as well or better than some more highly soluble salts, and gastric acid is not necessary for absorption if taken with meals 3.
- Potential adverse effects of calcium supplementation include gastrointestinal complaints, and high intakes (>1500 mg/d) may be associated with an increased risk of advanced and fatal prostate cancer 4.
- Calcium-alkali syndrome is a potential risk of long-term ingestion of calcium carbonate antacids, particularly in patients taking concomitant medications that may exacerbate hypercalcaemia 6.