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Deficiency/Mobility/Women

Calcium

Essential mineral that fills dietary calcium gaps and supports bone health, especially in older adults and low-intake diets.

Calcium

Calcium

71
score
A
evidence
Caution
risk

Proven Benefits

01Corrects low calcium intake
02Reduces preeclampsia risk
03Preserves bone density
04May lower fracture risk
05May reduce PMS symptoms
06May lower blood pressure

Chemical Forms

Recommended
  • Calcium citrate
  • Calcium carbonate
  • Calcium citrate malate
Avoid
  • Bone meal calcium (possible heavy metal contamination)
  • Oyster shell calcium (contamination variability)
  • Coral calcium (no proven advantage over carbonate)
Expert Note

Calcium citrate absorbs well with or without food and is preferred with low stomach acid or PPI use. Calcium carbonate is cheap and concentrated at about 40% elemental calcium, but it works best with meals. Bone, shell, and coral products offer no proven absorption advantage and have more contamination variability.

Protocol

Amount
300-600 mg elemental calcium
Frequency
Once daily or split into 2 doses if filling a larger gap
When
With meals if using calcium carbonate; calcium citrate can be taken with or without food. Keep single doses at or below 500-600 mg.

Condition-Based Dosing

Adults 19-50 with low dietary intake
Supplement only the gap needed to reach about 1000 mg/day total calcium from food plus supplements
Women over 50 or men over 70
Supplement only the gap needed to reach about 1200 mg/day total intake
Pregnant women with very low calcium intake
1000-1500 mg/day elemental calcium in 2-3 divided doses; some public-health guidelines use 1500-2000 mg/day
PPI use or reduced stomach acid
Use calcium citrate rather than carbonate at the same elemental dose

Safety & Limits

Upper Safe Limit
2000 mg/day total intake age 51+; 2500 mg/day age 19-50 (IOM UL)
Cycling
Safe for continuous use

Contraindications

Hypercalcemia or primary hyperparathyroidism — may worsen elevated calcium levels
Recurrent calcium kidney stones or hypercalciuria — may raise stone risk, especially if taken away from meals
Advanced chronic kidney disease — altered calcium/phosphate handling and vascular calcification risk
Sarcoidosis or other granulomatous disease — can raise active vitamin D and trigger hypercalcemia
Digoxin — hypercalcemia increases arrhythmia risk
Thiazide diuretics — reduce urinary calcium excretion and can raise calcium too much
Levothyroxine — calcium binds the drug and markedly reduces absorption; separate by 4 hours
Tetracycline or fluoroquinolone antibiotics — calcium chelates the drug and reduces absorption
Oral bisphosphonates — calcium blocks absorption if taken together

Synergies

Vitamin D3

Vitamin D increases intestinal calcium absorption and helps suppress excess parathyroid hormone, so low vitamin D can blunt the bone response to calcium.

Vitamin K2

Vitamin K2 helps activate osteocalcin and matrix Gla protein, which are involved in moving calcium into bone and away from soft tissue.

Avoid Combining With

  • ✕Iron supplements (separate by 2+ hours — competes for absorption)
  • ✕Zinc supplements (separate by 2+ hours — competes for absorption)
  • ✕Spinach, bran, and other high-oxalate/phytate meals (bind calcium and reduce absorption)
  • ✕Proton pump inhibitors with calcium carbonate (reduced absorption; citrate less affected)
  • ✕Vitamin D deficiency (blunts calcium absorption and bone response)
  • ✕Very large single doses over 500-600 mg (fractional absorption drops)
  • ✕High-sodium diets (increase urinary calcium losses)
  • ✕Heavy caffeine intake (slightly increases urinary calcium losses; matters more if intake is low)
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