Calcium Gluconate Ampule Content
A standard ampule of 10% calcium gluconate contains 1 gram (1,000 mg) of calcium gluconate in 10 mL, which provides only 93 mg (0.465 mEq) of elemental calcium—not 1 gram of elemental calcium. 1
Critical Distinction: Calcium Gluconate vs. Elemental Calcium
The confusion arises from the difference between the calcium salt and actual elemental calcium content:
- Each 10 mL ampule of 10% calcium gluconate contains 1,000 mg (1 gram) of the calcium gluconate salt 1
- However, this provides only 93 mg (0.465 mEq) of elemental calcium 1
- The FDA label explicitly states: "Each mL of Calcium Gluconate Injection, USP contains 100 mg of calcium gluconate...Each mL contains 9.3 mg (0.465 mEq) of elemental calcium" 1
Practical Dosing Implications
When prescribing or administering calcium gluconate, you must specify whether you're ordering:
- Calcium gluconate salt (the compound itself): 1 amp = 1 gram 1
- Elemental calcium (the actual calcium content): 1 amp = 93 mg or approximately 0.5 mEq 1
Each 10 mL vial of 10% calcium gluconate contains 2.2 mmol of elemental calcium 2, which is critical for calculating equivalent doses when switching between calcium salts.
Comparison with Calcium Chloride
Understanding this distinction becomes especially important when comparing calcium salts:
- Calcium chloride provides approximately 3 times more elemental calcium per volume than calcium gluconate 3
- For example, 10 mL of 7.35% calcium chloride contains 5 mmol of calcium, requiring only 4.4 mL to equal the elemental calcium in one 10 mL ampule of calcium gluconate 2
- The American Heart Association prefers calcium chloride over calcium gluconate in cardiac arrest due to more rapid increases in ionized calcium concentration 4
Common Pitfall to Avoid
Never assume "1 gram" means 1 gram of elemental calcium when ordering calcium gluconate—you're actually ordering 1 gram of the calcium gluconate salt, which contains only about 9% elemental calcium by weight 1. This 10-fold difference can lead to significant underdosing if not recognized.