Blood is the circulatory fluid that runs through most corporeal lifeforms in the universe. Its primary function is to carry nutrients and respiratory gases to cells and to remove waste products. Blood transfusions can only be undertaken between individuals with the same blood composition.
Many drugs need to be introduced into the bloodstream to take effect. Anesthetic agents, for instance, are intravenously administered.
When experimenting on crewmembers of the USS Enterprise-D, solanogen-based lifeforms slowly turned Lieutenant Edward Hagler's blood into a liquid polymer, thereby killing the officer. (TNG: "Schisms")
Blood chemistry is a term used to describe the composition of elements, chemicals, and other substances in a person's blood. The chemistry of the metal-protein complex of the component cells responsible for respiratory delivery influence the color of the blood.
Known colors and chemical compositions included:
- red (iron-based) – Human, Bajoran, Talaxian, Ocampa, Hirogen, Ilari, Gorn, Trill, Klingon (most appearances), Ferengi, Ennis, Jem'Hadar, Serosian, Mari, Nygean, Suliban, Vori, Eska, Denobulan, Xindi-Primate (ENT: "The Council"), most humanoids
- reddish-green (iron-copper composite based) – Acamarian
- green (copper-based) – Vulcan, Romulan, chameloid
- blue – Andorian, Bolian
- pink, lavender – Klingon (in some cases)
- yellow – Void alien (Fantome's people), Species 8472, Na'kuhl
- brown – Cardassian
- white – Tamarian
Bolians had a blood chemistry very different from that of other species, especially Vulcans. If a blood transfusion was given from a Vulcan to a Bolian it would result in the death of the Bolian. There were instances when artificial blood was unavailable and existing blood cells were genetically altered for inter-species transfusions to be successful. (VOY: "Prototype")
In 2367, Dr. Beverly Crusher noticed that Lieutenant Commander Susanna Leijten's blood chemistry was slightly off after beaming back from the surface of Tarchannen III. It was later discovered that she was in fact being transformed into another lifeform. (TNG: "Identity Crisis")
When creating the Jem'Hadar, the Founders deliberately omitted a key isogenic enzyme from their blood chemistry, giving it to them in the form of ketracel-white. The Jem'Hadar needed to keep taking the white or they would die, thus ensuring their loyalty to the Founders. (DS9: "The Abandoned")
In 2371, the USS Voyager's EMH discovered that Ensign Seska's blood chemistry was not consistent with that of a Bajoran. Her cover story was that she suffered from Orkett's disease as a child during the Occupation of Bajor, and that she had received a bone marrow transplant from a Cardassian woman named Kattell. (VOY: "State of Flux")
- Blood bank
- Blood plasma
- Blood screening
- Blood soup
- Rokeg blood pie
- Blood type
In Star Trek VI: The Undiscovered Country, Klingon blood was portrayed as pink and lavender, while in TNG and DS9 it was red. The supposed reason for this is that having floating red blood all over the ship was considered too violent, and would have given the movie a more extreme rating than would be appropriate for the target audience. Pink blood makes it obvious at a glance that the violence is simulated, not real. The change in blood may have been another side effect of the Klingon augment virus.
Several non-canon sources have suggested that the bases of blue-blooded aliens blood are silicon and cobalt. This would be logical as some real-life creatures have blue blood based on molecules other than iron and copper.