• We know that calcium chloride (CaCl2) provides 3 times more elemental calcium than an equivalent amount of calcium gluconate.
  • So, CaCl1 gm = calcium gluconate 3 gm.


  1. Does CaClhave better bioavailability than calcium gluconate?
  2. Does calcium gluconate have a slower onset of action because it needs hepatic metabolism to release the calcium?


Calcium gluconate does NOT require hepatic activation to exert its effect.


Liver transplant patients [1]

  • Serum ionized calcium levels were measured in 15 hypocalcemic patients during the anhepatic stage of liver transplantation. Half received CaCl2 10 mg/kg, the other half received calcium gluconate 30 mg/kg.
  • Serum concentrations of ionized calcium were determined before and up to 10 min after calcium therapy.
  • Equally rapid increases in calcium concentration after administration of CaCland gluconate were observed, suggesting that calcium gluconate does not require hepatic metabolism for the release of calcium and is as effective as CaClin treating ionic hypocalcemia in the absence of hepatic function.

Children and dogs [2]

  • A weird randomized prospective study in both children and dogs compared ionization of CaCland calcium gluconate.
  • The authors conclude that equal elemental calcium doses of calcium gluconate (10%) and CaCl(10%) (approximately 3:1), injected over the same period of time:
    • Are equivalent in their ability to raise calcium concentration during normocalcemic states in children and dogs
    • The changes in calcium concentration following calcium administration are short-lived (minutes)
    • The rapidity of ionization seems to exclude hepatic metabolism as an important factor in the dissociation of calcium gluconate

Ferrets and in vitro human blood [3]

  • Equimolar quantities of CaCland calcium gluconate produced similar changes in plasma ionized calcium concentration when injected IV into anesthetized ferrets or when added to human blood in vitro.
  • In vivo changes were followed with a calcium electrode positioned in the animal’s aorta, and this showed that the ionization of calcium gluconate on its first pass through the circulation is as great as that of CaCl2.
  • This does not support the common suggestion that CaClis preferable to calcium gluconate because of its greater ionization.


As long as equivalent doses are used, calcium gluconate works as quickly (and to the same degree) as CaClto raise calcium concentration… without the same extravasation risk.



  1. Martin TJ, Kang Y, Robertson KM, Virji MA, Marquez JM. Ionization and hemodynamic effects of calcium chloride and calcium gluconate in the absence of hepatic function. Anesthesiology. 1990 Jul;73(1):62-5. PubMed PMID: 2360741.
  2. Cote’ CJ, Drop LJ, Daniels AL, Hoaglin DC. Calcium chloride versus calcium gluconate: comparison of ionization and cardiovascular effects in children and dogs. Anesthesiology. 1987 Apr;66(4):465-70. PubMed PMID: 3565811.
  3. Heining MP, Band DM, Linton RA. Choice of calcium salt. A comparison of the effects of calcium chloride and gluconate on plasma ionized calcium. Anaesthesia. 1984 Nov;39(11):1079-82. PubMed PMID: 6507824.
Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Leadership Team, ALiEM
Creator and Lead Editor, Capsules and EM Pharm Pearls Series
Attending Pharmacist, EM and Toxicology, MGH
Associate Professor of EM, Division of Medical Toxicology, Harvard Medical School
Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP


EM Pharmacist & Toxicologist @MassGeneralEM | Asst Prof @HarvardMed/@EMRES_MGHBWH | @ALiEMteam leadership | Capsules creator, ALiEMU | President, ABAT | #FOAMed