Heparin

Heparin is a medication and naturally occurring glycosaminoglycan. In cryonics, it is used as an anticoagulant (blood thinner). It is administered after the legal death. Heparin prevents the formation of blood clots that can interfere with blood circulation and cryoprotective perfusion.

Heparin loses effectiveness at low pH (pH < 6.7), so control of pH is important during a cryonics stabilization. This is why other anticoagulants are also important.