(covers information from several alternate timelines)
Blood was the circulatory fluid that runs through most corporeal lifeforms in the universe. Its primary function is to carry nutrients and respiratory gasses 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.
In 2004, a group of Xindi-Reptilians from the year 2153 began to synthesize a bio-weapon to use against Humankind in the future. They employed the service of Loomis to abduct eight individuals of different blood types and bring them to a warehouse on Carpenter Street, where the Reptilians would extract blood samples and use them in producing the viral toxin to be used for their bio-weapon. (ENT: "Carpenter Street")
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 an individual'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)
- Bajoran (DS9: "The Circle", "The Way of the Warrior")
- Denobulan (ENT: "Divergence")
- Ennis (DS9: "Battle Lines")
- Eska (ENT: "Rogue Planet")
- Ferengi (DS9: "The Ascent")
- Gorn (ENT: "In a Mirror, Darkly, Part II")
- Haliian (TNG: "Aquiel")
- Hirogen (VOY: "Prey", "Flesh and Blood")
- Human (ENT: "The Andorian Incident"; TNG: "The Arsenal of Freedom", "Skin of Evil"; Star Trek Generations; VOY: "Time and Again")
- Ilari (VOY: "Warlord")
- Jem'Hadar (DS9: "To the Death")
- Klingon (TNG: "Heart of Glory"; DS9: "The House of Quark"; Star Trek Generations)
- Ligonian (TNG: "Code of Honor")
- Makull's species (VOY: "Time and Again")
- Mari (VOY: "Random Thoughts")
- Nygean (VOY: "Repentance")
- Ocampa (VOY: "Caretaker")
- Rutian (TNG: "The High Ground")
- Serosian (VOY: "Revulsion")
- Suliban (ENT: "Storm Front, Part II")
- Talaxian (VOY: "Alliances", "Rise")
- Trill (DS9: "Rocks and Shoals", "Change of Heart"; Star Trek: Insurrection)
- Vori (VOY: "Nemesis")
- Xindi-Primate (ENT: "The Council")
- Most humanoids (TNG: "The Chase")
- reddish-green (iron-copper composite based)
- green (copper-based)
- pink, lavender
- orange (platinum-mercury based)
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, The Doctor, 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 Star Trek: The Next Generation and Star Trek: Deep Space Nine 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. Pink blood appears to have made a reappearance in Star Trek: Discovery, as it was seen in "Point of Light". See here for a more detailed discussion of Klingon blood color.
Brown blood – present in Cardassians – is only found in real life in the mollusc Pinna squamosa, which is similar to hemocyanin, but is based on manganese, instead of copper. Violet blood – present in Klingons – is found on certain molluscs, which is based on iron, but in a non-heme protein.
Unused scripted references
In the writers' first draft script of ENT: "Dear Doctor", the sight of blood, while Doctor Phlox was bandaging a laceration on Trip Tucker's hand, caused a large, tough-looking engineering officer standing nearby to suddenly faint, so Phlox then switched his focus to the felled giant.
Several non-canon sources have suggested that the bases of blue-blooded aliens' blood are silicon and cobalt. (citation needed • edit) This would be logical, as some creatures in reality have blue blood based on molecules other than iron and copper.