# What citrate is a common anticoagulant?

When I underwent plateletpheresis, something that the staff called "citrate" was added to my blood as an anticoagulant. Everything I can find about this product online refers to it as just "citrate". But from what little I know about chemical names, citrate is an ion, normally found not by itself but rather as magnesium citrate, potassium citrate, calcium citrate, vel sim.

What's the other half of this anticoagulant: which citrate is it?

Per the NIH:

ANTICOAGULANT CITRATE DEXTROSE A...
...
Citric Acid, anhydrous, USP 0.073 g
Sodium Citrate, dihydrate, USP 0.220 g
Dextrose, monohydrate, USP 0.245 g
Water for Injection, USP q.s.
pH: 4.5 – 5.5

They used the citrate ion in the form of citric acid and sodium citrate. The citric acid is for chleating calcium while the sodium citrate does this and acts as a buffer to prevent the citric acid from raising your blood pH too much when injected as this would be painful and hazardous. Sodium is naturally in your blood and will not interfere with action potentials and is a abundant and cheap ion to use in manufacturing so it makes a logical counter ion for the citrate buffer.

• Actually citric acid and sodium citrate form a buffer. Calcium chelates with citrate anion not citric acid per sey. However decreases citrate anion causes citric acid to ionize restoring the equilibrium between pH, citric acid and sodium citrate. – MaxW Oct 29 '18 at 19:11