Calcium Gluconate Elemental Calcium Content
One gram (1g) of calcium gluconate contains 93 mg of elemental calcium, commonly rounded to 90 mg in clinical practice. 1
Calcium Gluconate Composition
- Calcium gluconate contains approximately 9% elemental calcium by weight 1, 2
- A standard 10-mL ampule of 10% calcium gluconate contains 90-93 mg of elemental calcium 3, 1
- The FDA label confirms that each mL of Calcium Gluconate Injection contains 9.3 mg (0.465 mEq) of elemental calcium 2
Comparison with Other Calcium Salts
Calcium gluconate has a lower elemental calcium content compared to other calcium salts:
- Calcium gluconate: 9% elemental calcium 1
- Calcium lactate: 13% elemental calcium 1
- Calcium citrate: 21% elemental calcium 3
- Calcium acetate: 25% elemental calcium 1
- Calcium carbonate: 40% elemental calcium 3, 1
Clinical Applications
- When treating hypocalcemia following parathyroidectomy, calcium gluconate infusions are dosed based on elemental calcium content at 1-2 mg/kg/hour 3
- For post-parathyroidectomy management, if ionized calcium falls below normal (<0.9 mmol/L), calcium gluconate infusion should be initiated at 1-2 mg elemental calcium per kg body weight per hour 3
- In clinical practice, calcium gluconate is often preferred over calcium chloride in patients with abnormal liver function 1
Absorption Considerations
- Calcium gluconate is 100% bioavailable when administered intravenously 2
- For oral supplementation, calcium carbonate is more cost-effective but requires gastric acidity for optimal absorption 3
- Calcium citrate has better absorption when taken without food but provides less elemental calcium by weight 3
Important Clinical Considerations
- The maximum recommended oral dose of elemental calcium that should be taken at one time is 500 mg to optimize absorption 3, 4
- For intravenous administration, the rate of infusion significantly affects calcium levels - studies show that 1.6 g/h of calcium gluconate is more effective than 1.0 g/h in maintaining plasma ionized calcium during therapeutic plasma exchange 5
- When treating moderate to severe hypocalcemia (ionized calcium <1.0 mmol/L), higher doses of 2-4 g IV calcium gluconate may be required, though response rates vary significantly 6
Potential Adverse Effects
- Rapid administration of calcium gluconate can cause vasodilation, hypotension, bradycardia, cardiac arrhythmias, and cardiac arrest 7
- Extravasation of calcium gluconate can lead to severe tissue injury, particularly in pediatric patients 7
- ECG monitoring is recommended during calcium administration, especially in patients with hyperkalemia 7
Remember that the elemental calcium content of calcium gluconate (9%) is significantly lower than that of calcium carbonate (40%), which is important when calculating replacement doses for hypocalcemia or when prescribing calcium supplements 3, 1.