What is the recommended IV dose of calcium gluconate (calcium gluconate) for a patient with severe hypocalcemia?

IV Calcium Dosing for Severe Hypocalcemia Without Continuous Infusion

For severe symptomatic hypocalcemia when continuous infusion is not feasible, administer 4g of calcium gluconate IV over 4 hours (1g/hour), which provides approximately 360mg of elemental calcium and successfully corrects moderate to severe hypocalcemia in 95% of critically ill patients. 1

Dosing Algorithm Based on Severity

Moderate to Severe Hypocalcemia (ionized calcium <1.0 mmol/L or symptomatic)

• Administer 4g of calcium gluconate IV over 4 hours (infusion rate of 1g/hour) 1
• This regimen achieves ionized calcium >1.0 mmol/L in 95% of patients and >1.12 mmol/L in 70% of patients 1
• Approximately 50% of the administered dose (about 200mg elemental calcium) is retained in the exchangeable calcium space 2

Mild Hypocalcemia (ionized calcium 1.0-1.12 mmol/L)

• Administer 2g of calcium gluconate IV over 2 hours (infusion rate of 1g/hour) 3, 2
• This successfully normalizes ionized calcium in 79% of patients with mild hypocalcemia 3
• Retains approximately 80mg of elemental calcium in the exchangeable calcium space 2

Life-Threatening Hypocalcemia with Arrhythmias (Tumor Lysis Syndrome context)

• Administer calcium gluconate 50-100 mg/kg IV slowly with continuous ECG monitoring 4
• For a 70kg adult, this translates to 3.5-7g of calcium gluconate 4
• Critical caveat: Do NOT administer if phosphate levels are elevated due to risk of calcium-phosphate precipitation in tissues 4

Essential Elemental Calcium Content

Each 10mL ampule of 10% calcium gluconate contains only 90mg of elemental calcium 4, 5, meaning:

• 1g calcium gluconate = 90mg elemental calcium 4
• 2g calcium gluconate = 180mg elemental calcium 4
• 4g calcium gluconate = 360mg elemental calcium 4

Administration Guidelines

Infusion Rate and Monitoring

• Infuse at maximum rate of 1g/hour to minimize vessel irritation 3, 2, 1
• Administer through a secure IV line; never mix with phosphate or bicarbonate-containing solutions 4, 5
• Monitor ECG continuously during administration for bradycardia and arrhythmias 4, 6

Timing of Reassessment

• Check ionized calcium 10 hours after completion of infusion to assess efficacy 2
• Calcium levels plateau by 10 hours post-infusion without further decline 2
• During active treatment, measure ionized calcium every 4-6 hours 4

Critical Pre-Treatment Considerations

Correct Hypomagnesemia First

• Hypocalcemia cannot be adequately corrected without first addressing magnesium deficiency 6
• Hypomagnesemia is present in 28% of hypocalcemic patients and impairs both PTH secretion and end-organ PTH response 6
• Administer magnesium sulfate 1-2g IV bolus before calcium replacement in symptomatic patients 6

Assess Phosphate Levels

• If phosphate is elevated (particularly in tumor lysis syndrome), use extreme caution with calcium administration 4
• High phosphate increases risk of calcium-phosphate precipitation causing obstructive uropathy and tissue calcification 4
• Consider renal consultation if phosphate >5.5 mg/dL 4

Post-Parathyroidectomy Context (Special Scenario)

For post-parathyroidectomy patients with ionized calcium <0.9 mmol/L (<3.6 mg/dL):

• Initiate calcium gluconate infusion at 1-2 mg elemental calcium per kg body weight per hour 4
• For a 70kg patient, this equals approximately 70-140mg elemental calcium/hour = 0.8-1.6g calcium gluconate/hour 4
• Measure ionized calcium every 4-6 hours for first 48-72 hours, then twice daily until stable 4

Common Pitfalls to Avoid

Inadequate Dosing for Severity

• Do not use 1-2g doses for moderate to severe hypocalcemia (iCa <1.0 mmol/L) 3
• Only 38% of patients with moderate to severe hypocalcemia respond to 2g doses 3
• The 4g regimen is required for adequate correction in this population 1

Overcorrection Risk

• Mild hypercalcemia (iCa 1.34-1.38 mmol/L) occurred in 2 of 20 patients (10%) receiving 4g doses 1
• Monitor for hypercalcemia, particularly in patients with normal renal function 1

Line Compatibility

• Never administer calcium through the same IV line as sodium bicarbonate or phosphate-containing solutions 4, 5
• Precipitation will occur, rendering both medications ineffective 5

Infusion Rate

• Do not exceed 1g/hour infusion rate 3, 2, 1
• Faster rates increase vessel irritation and risk of cardiac complications 3, 2

Evidence Quality Note

The 4g dosing regimen for moderate to severe hypocalcemia is supported by prospective research in critically ill trauma patients 1, while guideline recommendations for tumor lysis syndrome and post-parathyroidectomy management provide context-specific dosing 4. The FDA label confirms elemental calcium content and administration parameters 5.