What is the treatment for a patient with hypocalcemia (low calcium levels)?

Treatment of Hypocalcemia

For acute symptomatic hypocalcemia, administer intravenous calcium gluconate or calcium chloride immediately, with calcium chloride preferred due to its higher elemental calcium content (270 mg vs 90 mg per 10 mL). 1, 2

Acute Symptomatic Hypocalcemia

Immediate IV calcium administration is required for patients with tetany, seizures, laryngospasm, bronchospasm, cardiac arrhythmias, or ionized calcium <0.8-0.9 mmol/L. 3, 1

IV Calcium Administration

• Calcium chloride 10% solution: 5-10 mL (270 mg elemental calcium per 10 mL) IV over 2-5 minutes for adults 1, 2
• Calcium gluconate 10% solution: 15-30 mL (90 mg elemental calcium per 10 mL) IV over 2-5 minutes as alternative 1, 4
• Pediatric dosing: Calcium gluconate 50-100 mg/kg IV slowly with continuous ECG monitoring 1, 2
• Administer via secure IV line (preferably central access) to prevent tissue necrosis from extravasation 1, 4
• Do NOT exceed infusion rate of 200 mg/minute in adults or 100 mg/minute in pediatric patients 4
• Monitor ECG continuously during administration for bradycardia or arrhythmias 1, 4

Continuous Infusion for Severe Cases

• Initial rate: 1-2 mg elemental calcium per kg body weight per hour, adjusted to maintain ionized calcium 1.15-1.36 mmol/L (normal range) 1
• Dilute to concentration of 5.8-10 mg/mL in 5% dextrose or normal saline 4
• Monitor ionized calcium every 4-6 hours initially, then every 1-4 hours during continuous infusion 1, 4

Critical Cofactor: Magnesium Correction

Check and correct hypomagnesemia FIRST—hypocalcemia cannot be adequately corrected without adequate magnesium, as hypomagnesemia impairs PTH secretion and causes end-organ PTH resistance. 1, 2

• Hypomagnesemia is present in 28% of hypocalcemic ICU patients 1
• Administer magnesium sulfate 1-2 g IV bolus immediately for symptomatic patients before calcium replacement 2
• For chronic management: oral magnesium oxide 12-24 mmol daily 2

Chronic/Asymptomatic Hypocalcemia

For corrected total calcium <8.4 mg/dL (2.10 mmol/L) without severe symptoms, initiate oral calcium supplementation with calcium carbonate plus vitamin D. 3

Oral Calcium Supplementation

• Calcium carbonate 1-2 g three times daily (preferred due to high elemental calcium content, low cost) 1, 2
• Calcium citrate is superior in patients with achlorhydria or taking acid-suppressing medications 2
• Limit individual doses to 500 mg elemental calcium to optimize absorption 2
• Total elemental calcium intake should NOT exceed 2,000 mg/day 3, 2
• Administer between meals or at bedtime for optimal absorption 2

Vitamin D Supplementation

• Measure 25-hydroxyvitamin D levels—if <30 ng/mL, supplementation is required 3, 1
• Vitamin D2 (ergocalciferol) 50,000 units orally monthly for 6 months for deficiency 1
• Daily maintenance: 400-800 IU vitamin D3 for chronic supplementation 2, 5
• Active vitamin D sterols (calcitriol 20-30 ng/kg/day or alfacalcidol 30-50 ng/kg/day) reserved for severe/refractory cases or when PTH >300 pg/mL in CKD stage 5 3, 1

Special Clinical Contexts

Chronic Kidney Disease (CKD)

• Treat hypocalcemia in CKD patients when corrected calcium <8.4 mg/dL AND plasma intact PTH is above target range for CKD stage 3
• Target corrected total calcium 8.4-9.5 mg/dL (lower end of normal range) 3
• Maintain calcium-phosphorus product <55 mg²/dL² 3
• Monitor corrected total calcium and phosphorus at least every 3 months 3, 2
• The 2025 KDIGO Controversies Conference shifted away from permissive hypocalcemia due to risks of severe hypocalcemia (muscle spasms, paresthesia, myalgia occurring in 7-9% of patients on calcimimetics) 2

Massive Transfusion/Trauma

• Maintain ionized calcium >0.9 mmol/L minimum (optimal 1.1-1.3 mmol/L) during massive transfusion 1, 2
• Hypocalcemia results from citrate-mediated calcium chelation from blood products (each unit contains ~3g citrate) 1, 2
• Citrate metabolism impaired by hypoperfusion, hypothermia, hepatic insufficiency—requires more aggressive replacement 1, 2
• Colloid infusions independently contribute to hypocalcemia beyond citrate toxicity 1, 2
• Monitor ionized calcium continuously during ongoing transfusion 1

Post-Parathyroidectomy

• Measure ionized calcium every 4-6 hours for first 48-72 hours, then twice daily until stable 2
• Initiate calcium gluconate infusion at 1-2 mg elemental calcium/kg/hour if ionized calcium <0.9 mmol/L 2
• Transition to oral calcium carbonate 1-2 g TID plus calcitriol up to 2 mcg/day when oral intake possible 2

22q11.2 Deletion Syndrome

• 80% have lifetime history of hypocalcemia due to hypoparathyroidism—may arise or recur at any age despite apparent childhood resolution 2
• Daily calcium and vitamin D supplementation recommended for all adults 2
• Heightened surveillance during biological stress (surgery, childbirth, infection, pregnancy) 2
• Avoid alcohol and carbonated beverages (especially colas) as they worsen hypocalcemia 2

Critical Pitfalls to Avoid

• NEVER mix calcium with sodium bicarbonate in same IV line—causes precipitation 1, 2
• Do NOT mix calcium gluconate with ceftriaxone—forms precipitates; contraindicated in neonates ≤28 days 4
• Avoid calcium administration when phosphate levels are high (risk of calcium-phosphate precipitation in tissues) 2
• Beware of overcorrection—iatrogenic hypercalcemia can cause renal calculi and renal failure 1, 2
• Standard coagulation tests may appear normal despite significant hypocalcemia-induced coagulopathy (samples are citrated then recalcified before analysis) 1
• Correction of acidosis may worsen hypocalcemia (acidosis increases ionized calcium levels) 1
• In CKD patients, do NOT use calcium-based phosphate binders when corrected calcium >10.2 mg/dL or PTH <150 pg/mL 2

Monitoring Requirements

• Acute setting: Ionized calcium every 4-6 hours initially, then every 1-4 hours during continuous infusion 1, 4
• Chronic management: Corrected total calcium and phosphorus every 3 months 3, 2
• Monitor magnesium, PTH, and creatinine regularly in chronic hypocalcemia 2
• Assess 25-hydroxyvitamin D annually once replete 3