How do you replete calcium?

How to Replete Calcium

Prioritize dietary calcium sources (dairy products, fortified foods) to reach 1000-1200 mg/day based on age and sex, and only use oral supplements when dietary intake is inadequate; reserve intravenous calcium exclusively for acute symptomatic hypocalcemia. 1, 2

Assess Current Calcium Status and Requirements

• Daily calcium requirements: 1000 mg/day for women 19-50 years and men 19-70 years; 1200 mg/day for women >50 years and men >70 years 1
• Calculate total current intake from diet plus any existing supplements 1
• Upper limit warning: Do not exceed 2000-2500 mg/day total intake (diet plus supplements) due to risks of nephrolithiasis and potential cardiovascular events 1, 2

Dietary Repletion (First-Line Approach)

Dietary sources are strongly preferred over supplements for calcium repletion. 1, 2, 3

• Dairy products provide the highest bioavailable calcium: milk (240 mg per 200 mL), hard cheese (220 mg per 30g), yogurt (200 mg per 120g) 1
• Non-dairy sources include: sardines with bones (258 mg per half tin), kale (100 mg per 67g), calcium-fortified soy milk (240 mg per 200 mL) 1
• Green leafy vegetables and legumes provide calcium but in lower amounts and with reduced bioavailability due to oxalates and phytates 4

Oral Calcium Supplementation (When Dietary Intake Inadequate)

Choosing the Right Supplement Formulation

For patients with normal gastric acid production:

• Calcium carbonate is the preferred first choice due to 40% elemental calcium content and cost-effectiveness 1, 2, 5
• Must be taken with meals to optimize absorption (requires gastric acidity) 1, 2
• Common side effects include constipation and bloating 1

For patients with achlorhydria, GERD, or taking acid-reducing medications (PPIs, H2-blockers):

• Calcium citrate is the preferred formulation despite lower elemental calcium content (21%) 6, 2, 5
• Can be taken without food; absorption independent of gastric acidity 6, 2
• Causes fewer gastrointestinal side effects than calcium carbonate 6

Dosing Strategy for Oral Supplements

• Maximum single dose: 500-600 mg elemental calcium to optimize absorption 2, 5
• If total supplementation exceeds 500 mg/day, divide into multiple doses throughout the day 1, 2
• Typical calcium carbonate dosing: One or two 500-mg tablets two to three times daily with meals 1
• Typical calcium citrate dosing: One or two 950-1000 mg tablets two to three times daily 1

Special Population Considerations

CKD patients (stages 3-4):

• Target total elemental calcium intake of 800-1000 mg/day (including dietary, supplements, and calcium-based binders) 1
• Adjust based on concurrent vitamin D analog and calcimimetic use to avoid hypercalcemia 1

Athletes and those with high sweat losses:

• Consider higher intake of 1500 mg/day, particularly in hot environments or with relative energy deficiency 1

Intravenous Calcium Repletion (Acute Symptomatic Hypocalcemia Only)

IV calcium is reserved exclusively for acute symptomatic hypocalcemia and should never be used for routine repletion. 2, 7, 8

IV Calcium Formulations

Calcium gluconate (preferred for peripheral IV):

• Contains 9.3 mg (0.47 mEq) elemental calcium per mL of 10% solution 8
• Administer via secure IV line (bolus or continuous infusion) 8
• Adult dosing: Individualize based on severity; measure serum calcium every 4-6 hours during intermittent infusions, every 1-4 hours during continuous infusion 8
• Pediatric dosing: Individualize within recommended range based on severity 8

Calcium chloride (central or deep vein only):

• Contains 27 mg (1.4 mEq) elemental calcium per mL of 10% solution 7
• Administer only by slow IV injection (not exceeding 1 mL/min), preferably in central or deep vein 7
• Adult dosing: 200 mg to 1 g (2-10 mL) at intervals of 1-3 days depending on response 7
• Pediatric dosing: 2.7-5.0 mg/kg hydrated calcium chloride (0.027-0.05 mL/kg of 10% solution) 7

Critical IV Administration Precautions

• Cardiac monitoring required: Risk of arrhythmias, bradycardia, and cardiac arrest with rapid administration 8
• Contraindicated with concurrent ceftriaxone in neonates due to fatal precipitate formation 8
• Extreme caution with cardiac glycosides: Synergistic arrhythmias may occur; use slow administration with ECG monitoring if concurrent therapy necessary 8
• Extravasation risk: Can cause tissue necrosis, ulceration, and calcinosis cutis; immediately discontinue if extravasation occurs 8

Common Pitfalls to Avoid

• Do not recommend calcium carbonate to patients with significant GERD or those on PPIs as it may worsen symptoms and has poor absorption 6
• Never exceed 500 mg elemental calcium per dose as absorption efficiency decreases with higher single doses 2, 5
• Avoid total intake >2000-2500 mg/day due to increased risk of kidney stones and potential cardiovascular events 1, 2
• Do not use IV calcium for routine repletion or chronic hypocalcemia; this is for acute symptomatic cases only 2
• Monitor for drug interactions: Calcium reduces response to calcium channel blockers and may cause hypercalcemia when combined with vitamin D, thiazides, or estrogen 8