Synth-blood is an artificial supplement for varying types of blood.
During the Great and Brood War, plenty of Protoss Dragoons were destroyed. Most of the technology salvaged was dedicated to life support. While going over the support systems, Terran scientists came across a container of blue liquid. Further examinations found that it was a synthetic substance which mimics the bodily functions of Protoss blood. After some time, researchers found a way to duplicate and adapt the substance for Terran medical use. Synth-blood is used as a blood substitute when patients need quick transfusions. Synth-blood also contains drugs that prevent the subjects own immune system from rejecting it. Similar to O-type blood, synth-blood can be given to any Terran.
Medics often carry SyntheGel, a concentrated version of synth-blood, in their med kits. SyntheGel is a thick, viscous substance that become more fluid as it heats up to Terran body temperature. Due to the ease of manufacturing synth-blood, it is found in nearly all Dominion Hospitals.