Citrate binds ionized calcium, resulting in decreased ionized calcium.

Citrate binds ionized calcium, resulting in decreased ionized calcium.

• A. True
• B. False
• C. Not sure
• D. Not specified

Answer: (A)

Citrate acts as a calcium chelator, binding Ca2+ to form calcium-citrate complexes and thereby lowering the amount of free, ionized calcium in the plasma. Ionized calcium is the biologically active portion that controls neuromuscular and cardiovascular activity, so when citrate chelates calcium, those active calcium levels drop. In clinical practice, this mechanism explains why citrate is used as an anticoagulant and why large amounts of citrate can transiently cause hypocalcemia until citrate is metabolized (primarily by the liver) and calcium is freed back into the ionized pool. Total calcium may not immediately reflect this drop because the bound calcium is still present as a complex rather than free, but the ionized portion—the functional calcium—decreases.

Citrate acts as a calcium chelator, binding Ca2+ to form calcium-citrate complexes and thereby lowering the amount of free, ionized calcium in the plasma. Ionized calcium is the biologically active portion that controls neuromuscular and cardiovascular activity, so when citrate chelates calcium, those active calcium levels drop. In clinical practice, this mechanism explains why citrate is used as an anticoagulant and why large amounts of citrate can transiently cause hypocalcemia until citrate is metabolized (primarily by the liver) and calcium is freed back into the ionized pool. Total calcium may not immediately reflect this drop because the bound calcium is still present as a complex rather than free, but the ionized portion—the functional calcium—decreases.