Management of Hypocalcemia
For symptomatic hypocalcemia, administer intravenous calcium chloride 10 mL of 10% solution (270 mg elemental calcium) immediately with continuous ECG monitoring, as calcium chloride delivers three times more elemental calcium than calcium gluconate and is the preferred agent for acute correction. 1
Acute Symptomatic Hypocalcemia (Life-Threatening)
Immediate Assessment and Stabilization
Check magnesium first – hypomagnesemia is present in 28% of hypocalcemic patients and must be corrected before calcium replacement will be effective, as low magnesium impairs PTH secretion and creates end-organ PTH resistance. 1, 2
If magnesium is <1.0 mg/dL, administer magnesium sulfate 1–2 g IV bolus immediately before calcium replacement. 1
Symptoms requiring immediate IV calcium include tetany, seizures, laryngospasm, bronchospasm, cardiac arrhythmias, QT prolongation >500 ms, or ionized calcium <0.75 mmol/L. 1, 2
Intravenous Calcium Replacement
Calcium chloride 10% solution: 10 mL (270 mg elemental calcium) IV over 2–5 minutes is the first-line agent for symptomatic hypocalcemia. 1
Calcium chloride is preferred over calcium gluconate because 10 mL of 10% calcium chloride contains 270 mg elemental calcium versus only 90 mg in 10 mL of 10% calcium gluconate. 1
If calcium chloride is unavailable, use calcium gluconate 10% solution: 15–30 mL IV over 2–5 minutes. 1
Administer via a central line when possible to avoid severe tissue necrosis if extravasation occurs. 1
Continuous ECG monitoring is mandatory during IV calcium administration to detect QT interval changes, bradycardia, and arrhythmias. 1, 3
Critical Safety Considerations
Never administer calcium through the same IV line as sodium bicarbonate – precipitation will occur. 1, 4
Use extreme caution when phosphate is elevated (>5.5 mg/dL) – high phosphate increases the risk of calcium-phosphate precipitation in tissues and kidneys; lower phosphate first with non-calcium-containing binders before aggressive calcium replacement. 1
If the patient is on cardiac glycosides (digoxin), calcium must be given slowly in small amounts with close ECG monitoring because synergistic arrhythmias may occur. 1, 4
Ongoing Monitoring During Acute Treatment
Measure ionized calcium every 4–6 hours during intermittent infusions and every 1–4 hours during continuous infusions. 1
For post-parathyroidectomy patients, measure ionized calcium every 4–6 hours for the first 48–72 hours, then twice daily until stable. 1
If ionized calcium falls below 0.9 mmol/L, start a calcium gluconate infusion at 1–2 mg elemental calcium per kg per hour, titrating to maintain ionized calcium between 1.15 and 1.36 mmol/L. 1
Asymptomatic or Mild Hypocalcemia
When to Treat
Treat when corrected total calcium is <8.4 mg/dL (2.10 mmol/L) AND intact PTH is above the target range for the patient's CKD stage. 1
In CKD stages 3–4, treat when PTH is >70 pg/mL (stage 3) or >110 pg/mL (stage 4). 1
In CKD stage 5 (dialysis), treat when PTH is >300 pg/mL. 1
The 2025 KDIGO Controversies Conference shifted away from permissive hypocalcemia in CKD patients, especially those on calcimimetics, because severe hypocalcemia occurs in 7–9% of such patients and is associated with muscle spasms, paresthesia, and myalgia. 1
Oral Calcium Supplementation
Calcium carbonate 1–2 g three times daily (providing 1,200–2,400 mg elemental calcium per day) is the preferred first-line oral supplement due to its high elemental calcium content (40%), low cost, and wide availability. 1
Calcium citrate is superior in patients with achlorhydria or those taking acid-suppressing medications. 1
Limit individual doses to 500 mg elemental calcium to optimize absorption, and divide doses throughout the day with meals and at bedtime. 1
Total elemental calcium intake (dietary plus supplements) must not exceed 2,000 mg/day to prevent hypercalciuria, nephrocalcinosis, and renal calculi. 1
Vitamin D Supplementation
Measure 25-hydroxyvitamin D; if <30 ng/mL, start ergocalciferol 50,000 IU orally once monthly for 6 months. 1
All adults with chronic hypocalcemia should receive daily vitamin D₃ supplementation of 400–800 IU. 1, 2
Active vitamin D metabolites (calcitriol 0.5–2 µg/day) are reserved for severe or refractory cases, particularly in hypoparathyroidism, and should be used under endocrinologist guidance. 1, 2
Calcitriol is indicated when intact PTH remains >300 pg/mL despite adequate vitamin D repletion in CKD stage 5 patients. 1
Target Calcium Levels
Maintain corrected total calcium in the low-normal range (8.4–9.5 mg/dL) in CKD stage 5 patients to reduce the risk of vascular calcification. 1
In CKD stages 3–4, maintain corrected total calcium within the normal laboratory range of 8.4–10.2 mg/dL. 1
Avoid over-correction – iatrogenic hypercalcemia can cause renal calculi, nephrocalcinosis, and renal failure. 1, 2
Monitoring Requirements
Measure corrected total calcium and phosphorus at least every 3 months during chronic supplementation. 1
Regularly monitor pH-corrected ionized calcium, magnesium, PTH, and creatinine concentrations. 1, 2
Keep the calcium-phosphorus product <55 mg²/dL² to prevent metastatic calcification. 1
Monitor urinary calcium excretion to detect hypercalciuria, which increases the risk of nephrocalcinosis and renal calculi. 1
Special Clinical Scenarios
Massive Transfusion
Monitor ionized calcium continuously during massive transfusion – each unit of blood products contains approximately 3 g of citrate that binds calcium. 1
Citrate metabolism may be impaired by hypoperfusion, hypothermia, and hepatic insufficiency, requiring more aggressive calcium replacement. 1
Hypocalcemia within the first 24 hours of critical bleeding predicts mortality with greater accuracy than fibrinogen, acidosis, or platelet count. 1
Tumor Lysis Syndrome
- Use extreme caution with calcium replacement when phosphate is elevated – administer calcium gluconate 50–100 mg/kg IV slowly with ECG monitoring only if symptomatic. 1
Patients with 22q11.2 Deletion Syndrome
80% have a lifetime history of hypocalcemia due to hypoparathyroidism, which may arise or recur at any age despite apparent childhood resolution. 1, 2
Daily calcium and vitamin D supplementation is recommended for all adults with this condition. 1
Avoid alcohol and carbonated beverages (especially colas) as they can worsen hypocalcemia. 1
Targeted calcium monitoring is critical during periods of biological stress (surgery, childbirth, infection). 1, 2
Dialysis Patients
Do not use calcium-based phosphate binders when corrected serum calcium is >10.2 mg/dL or when plasma PTH levels are <150 pg/mL on two consecutive measurements. 1
Adjust dialysate calcium concentration based on the patient's calcium needs; standard dialysate calcium of 2.5 mEq/L (1.25 mmol/L) permits use of calcium-based binders with minimal calcium loading. 1
For intensive hemodialysis regimens, use dialysate calcium of ≥1.50 mmol/L (3.0 mEq/L) to maintain neutral or positive calcium balance. 1
Common Pitfalls to Avoid
Do not attempt to correct calcium without first checking and correcting magnesium – calcium replacement will fail without adequate magnesium levels. 1, 5
Do not aggressively correct mild asymptomatic hypocalcemia without evaluating the full clinical context, including PTH, phosphorus, and the calcium-phosphorus product. 1
Do not use calcium-based therapy when serum phosphorus exceeds 5.5 mg/dL – the high phosphate level markedly increases the risk of calcium-phosphate precipitation. 1
Do not administer calcium and sodium bicarbonate through the same IV line – precipitation will occur. 1, 4
Do not overlook extravasation – if extravasation occurs or clinical manifestations of calcinosis cutis are noted, immediately discontinue IV administration at that site. 1, 4