Calcium Repletion: A Comprehensive Approach
The preferred approach to calcium repletion is through dietary sources, particularly dairy products, with supplements used only when dietary intake is inadequate to meet recommended daily requirements. 1
Recommended Dietary Calcium Intake
Daily calcium requirements vary by age and sex:
- Adults 19-50 years and men 51-70 years: 1000 mg/day
- Women over 50 and men over 70 years: 1200 mg/day
- Adolescents and young adults (11-24 years): 1200-1500 mg/day
- Upper intake limit: 2000-2500 mg/day (2000 mg/day for those >50 years) 1
Step 1: Assess Current Calcium Intake
Calculate approximate dietary calcium intake:
- Assume 300 mg/day from non-dairy sources (vegetables, grains)
- Add dairy intake using this guide:
- 1 cup (240 mL) milk: 300 mg calcium
- 1 oz (30 g) hard cheese: 200 mg calcium
- 1 cup (240 mL) yogurt: 400 mg calcium 1
Step 2: Optimize Dietary Calcium Sources
Dietary calcium sources are preferred over supplements because:
- They provide additional essential nutrients
- Some evidence suggests better absorption from certain foods
- Fewer adverse effects compared to supplements 1, 2
Key calcium-rich foods:
- Dairy products (milk, yogurt, cheese): 200-400 mg per serving
- Green leafy vegetables (kale, broccoli): 34-100 mg per serving
- Calcium-fortified foods (orange juice, plant milks): variable content 1
Step 3: Consider Calcium Supplements When Necessary
If dietary intake is insufficient, choose an appropriate supplement:
| Calcium Salt | Elemental Calcium | Considerations |
|---|---|---|
| Calcium carbonate | 40% | Most cost-effective; take with meals as gastric acidity improves absorption; may cause constipation and bloating [1,3] |
| Calcium citrate | 21% | Better absorbed without food; good alternative for patients with gastrointestinal symptoms or on acid-reducing medications [1,3] |
| Calcium gluconate | 9% | Rarely used for oral supplementation due to low elemental calcium content [3] |
| Calcium lactate | 13% | Rarely used for oral supplementation [3] |
Step 4: Optimize Supplement Administration
- For doses >500 mg elemental calcium daily, divide into multiple doses to improve absorption and minimize gastrointestinal side effects 1
- Take calcium carbonate with meals to optimize absorption 1
- Calcium citrate can be taken with or without food 1
- Avoid taking calcium supplements with foods high in phytates (bran cereal) or oxalates (spinach) which reduce bioavailability 1
Step 5: Consider Vitamin D Status
- Adequate vitamin D is essential for optimal calcium absorption 1, 3
- Standard dose: 400-1000 IU daily of cholecalciferol or ergocalciferol 3
- Consider active vitamin D metabolites (calcitriol, alfacalcidol) for patients with impaired vitamin D metabolism 3
Special Considerations
Intravenous Calcium Administration (for severe hypocalcemia)
- Calcium gluconate: 9.3 mg (0.465 mEq) elemental calcium per mL 4
- Administer through a central venous catheter when possible to minimize extravasation risk 3
- Monitor serum calcium during intermittent infusions every 4-6 hours and during continuous infusion every 1-4 hours 4
Potential Adverse Effects
- Gastrointestinal: constipation, bloating, nausea 1
- Increased risk of nephrolithiasis with supplements (not with dietary calcium) 1
- Potential cardiovascular concerns with high-dose supplements, though evidence is inconsistent 1
Common Pitfalls to Avoid
- Exceeding the upper intake limit of 2000-2500 mg/day
- Relying solely on supplements when dietary sources are available
- Taking calcium supplements with foods that impair absorption
- Neglecting vitamin D status when repleting calcium
- Failing to divide large supplement doses
- Using calcium chloride for oral supplementation (may cause metabolic acidosis) 1
By following this structured approach to calcium repletion, you can effectively optimize calcium status while minimizing potential adverse effects.