Although most of the real world gets by quite peacefully with the more common blood types, in the world of entertainment only the rarest will do; if a character's blood type is mentioned, you can bet, if not your bottom dollar, then certainly one of the lower ones that it's going to be rare and special.
In the early twentieth century, red blood cells were first given the most common classifications: O, A, B and AB. Three decades later the Rhesus factor was also discovered, marking any blood as RH positive (+) or RH negative (-), and woe to you if you get a transfusion of the wrong RH. (Only applicable if the receiver is RH negative. In RH- blood there is no antigen for the RH+ body to recognize and fight, whereas the RH- body will attack RH+ blood.) Now, O red cells can be given to anyone, and AB can receive any type of red blood cells. So a really rare blood type for receiving a red cell donation would be O- (because the only type they can tolerate is another O-), B-, then A- (B- is the rarest of the three, but can tolerate the more common O-, as can A-).
With plasma, it's the other way around. The plasma of group O people contains antibodies to both A and B blood group substances, which is why they have a reaction if they receive those types. So giving O plasma to an A patient may result in a minor reaction as the donated antibodies attack the recipient's cells. AB plasma has neither antibody, so it can be given to anyone.
Blood in fiction really comes in only two types: universal donor (rare) and special needs (common), so that blood banks are overtaxed whenever the plot requires. Compare to reality, where Type O is the most common and the negative variant can be received by almost everyone, and AB- is the least common but unlike in fiction, where that means the person needs to look far and wide for another AB- donor, in real life a person with AB- blood can receive blood from any other negative type. In fact having B- blood gives you less types of blood you can receive than AB- and is not that much more common at all. Rh factor works the same way; people negative for it can only take negative blood but people positive can take both. Note that in ideal medical conditions, doctors do prefer to match blood type as exactly as possible, especially when doing organ transplants to reduce the risk of rejection, but in a life-or-death situation any compatible blood type will do. For white people, only about 16% of people are Rh negative.
The situation of needing rare blood types is an actual problem that happens in medicine, but it is almost never ABO or Rh type and usually deals with other red cell antigens, most of which are rarely mentioned outside the blood banking community. Some of these are extremely rare or are only present in certain ethnic groups. According to The Other Wiki, there are two dozen factors.
By the way, how many of us actually know their blood types right off the top of their head? Everyone in fiction seems to know. This can be justified in the case of anime due to Asian beliefs in Personality Blood Types, or in military oriented works due to many militaries including the information on the identification tags for their personnel. Blood donors will also usually know, having been told by the collection site at which they donated. As should women who are or have previously been pregnant, since the +/- factors in blood have a chance to cause catastrophic Rh incompatibility, potentially killing the developing child. There is also some Truth in Television here, since people with exceedingly rare blood types are the most likely to be told/remember their type simply because it's interesting. In general, you don't need to know your blood type, or keep that information on your person. No doctor would trust your information and risk a medical malpractice suit.
You can thank Dr. Charles Drew for discovering and codifying blood types. He discovered how to match up blood types and also came up with a method for storing blood for up to 14 days (previously it was no good after 48 hours) saving thousands of lives in WWII.
Not to be confused with Did Not Do the Bloody Research.
- In general, many anime and manga series will list their characters' blood types in supplementary materials, due to the afformentioned Asian beliefs in Personality Blood Types. Given that something like 99% of people in Japan are Rh positive (+) the system is only based on the four antigen combinations. Functionally assume everyone is Rh positive unless specified to be otherwise.
- Though it's only mentioned in supplemental materials, the fact that Mashiro in My-HiME has AB- blood in Japan, a country mostly without the negative RH factor, serves as an early clue that she's not quite what she appears to be. Not to mention the fact that she shares her blood type with Fumi, along with her birthday and voice actress.
- Bombay blood type appears in Yakitate!! Japan, used to show that Pierrot Bolnez and the king of Monaco are related.
- In Detective Conan, Conan's blood type is a major plot point during the Desperate Revival arc. Ran offers to donate blood to Conan, after he is shot earlier in the arc, without stopping to check his blood type, implying she knows he is Shinichi.
- Eisuke Hondo is a universal donor. This is important because his sister, having donated blood to him, also had to be blood type O, meaning that she couldn't be Rena Mizunashi, who has blood type AB. Except, as it turns out, she is; Eisuke's blood type changed to AB when she donated some bone marrow to him due to his leukemia.
- Angels in Neon Genesis Evangelion must be identified on the computers as having Blood Type BLUE before the Evas can attack them. The fact that the majority of Angels are several stories tall and shoot lasers isn't enough of a giveaway.
- Word of God is that "Blood pattern Blue!" is a shoutout to an old Japanese scifi B-movie, in which people who see UFO's have their blood turn blue (then get discriminated against). It has nothing to do with the plot of Eva, its just an in-joke. Moreover they don't actually call it "Blood type" in the sense of AB- or O+, but "Blood Wave-Pattern" which is made up technobabble.
- Like many anime series, the blood types of the main characters are listed in the supplementary materials, and fit the "blood type theory of personality" very accurately. Shinji is Type A, and is thus weak and submissive (a majority of people in Japan are actually Type A). Asuka is the only Type O, and accordingly is a hothead (it does make sense that as she is from Germany and the only non-Japanese person on the show, she has an uncommon blood type for Japan). Misato is even wounded in one episode and they display that her specific blood type she's getting in a transfusion is "AO", although there is no functional difference between "AA" and "AO" because A is dominant.
- That's not entirely true, as human chimeras do exist carrying two distinct blood types, like AO. As if Eva weren't complicted enough.
- Rebuild of Evangelion complicates this further: an onscreen graphic notes that Unit-01 is BLUE A* while Sachiel is BLUE 04, being the fourth Angel in this continuity. Shamshel and Ramiel keeps this numbering too.
- Ryouhei Sumi in Future GPX Cyber Formula once gets into an accident which caused some serious loss of blood in one filler episode. His blood type (AB) is not shown, but is mentioned to be very rare, as it is difficult enough to use transfusion in case of an emergency—to the level that even though he got better, he gave up auto racing because of his blood type due to safety reasons.
- In the 70's Shoujo horror/romance manga Akuma no Hanayome (Bride of Deimos), there's a story in the manga about the main character Minako's friend who was horribly disfigured in a car accident and Deimos made a deal to Minako that he can fix her friend's face if she agrees to marry him. She refuses his offer, so instead, she made a deal with the friend—who turns out to be a vampire, as she needed RH AB-Negative blood of young girls to keep her face from rotting once a month.
- This has recently become a significant plot point in One Piece, where Sanji is revealed to have a rare blood type, and Chopper runs out of spare blood for transfusions because Sanji keeps having incredible nose bleeds, prompting a crisis when the racist Fishmen refuse to donate blood.
- This gets played about with a bit more later in the same arc, when Luffy is in dire need of a blood transfusion after his fight with Hody. No one else in the Straw Hats have the same blood type as Luffy, but considering how small Luffy's crew is(and how one member doesn't even have blood), this is fairly believable. Several people in the nearby crowd do have the same blood type, and Luffy's suffered blood loss at least a few times with it being dealt with offscreen, so it's implied to be not particularly rare; the Straw Hats just didn't have another ready source on hand at that particular moment.
- One story in Black Jack features a rich businessman with a rare blood type. When he desperately needs a transfusion after an accident, he pays Black Jack a significant sum of money for help, and a construction worker is found who matches him. Several months later, the construction worker is himself injured. In order to help him, the businessman misses a vital plane flight and winds up losing his entire company. In the end, the best he can say is that at least he saved a life--until Black Jack gives him a check for most of the money he initially paid him.
- In Hellblazer, Brendan Finn is "O Guinness positive", which makes him a "universal recipient". No, it's not magic, he just drinks a lot.
- In the Yoko Tsuno album La Frontière de la Vie, the entire plot evolves from how a child has an exceedingly very rare blood.
- In the infamous "I am Curious (Black)" Superman comic, Lois Lane turns black for a day (for a story on racism) and befriends a grassroots, er, community leader (it's never clarified what he is, he just stands on a soapbox, rants to a crowd, and later breaks up a drug deal), who hates him some crackers. When the man needs a blood transfusion, the doctor at the black hospital proclaims that the man is O-, but, horror of horrors, the hospital doesn't have enough money to carry all blood types! Luckily Lois, who has returned to her "white lady" status, is O-, and with the blood transfusion they bridge the gap of racism.
- Bruce Almighty sees Jennifer Aniston proudly declare herself to be AB+ , a "very rare blood type".
- Apparently not too rare seeing as Bruce has the same blood type
- The abducted victims in The X-Files: I Want To Believe all had AB- blood. It turns out that this is because the kidnapper is trying to perform a full-body transplant.
- The Greatest Show On Earth, winner of the Academy Award for Best Picture in 1952, involves a train wreck with a victim that needs a blood transfusion. Guess what his blood type is? (And, of course, the fact that his AB- blood could accept a transfusion from ANY Rh negative donor is completely unknown to the doctor who is treating him. The donor has to be AB-, or nothing!)
- Averted in Some Like It Hot, where it is reiterated that one of the main characters is a type O.
- Also averted in All The Young Men, a long-forgotten Korean War military drama featuring a young Sidney Poitier. His white CO needs a transfusion and is Type O, but they're all out of bottled O. Guess who else is Type O. This was considered daring in 1960.
- Drives the plot in Made in America. The daughter learns her blood group in a biology class at school. She happens to know the blood group of her mother and her dead father and realises that she can't be her father's daughter. Whoopi Goldberg admits that in fact she wasn't pregnant when her partner died and used a sperm donor and pretended (even to herself) that it was her partner's child.
- A major plot point of John Q was that the title character's son was a rare bloodtype and needs a heart transplant. Meanwhile, a woman dies in a car wreck of the same bloodtype, and they eventually use her heart.
- AB- figures in the plot of Robert A. Heinlein's I Will Fear No Evil, which involves the protagonist's brain being transplanted into a new body. Part of the plot setup is the rarity of the AB- blood type; the protagonist is shocked when his body donor was actually someone he knew well.
- In Breaking Dawn The Cullens keep a refrigerator full of blood in their house just in case Bella ever needs a transfusion. Naturally it's the very rare O-.
- Is a plot point in a Nancy Drew file.
- In An Echo In The Bone, one character, Ian, has it suggested that his wife's miscarriage was due to issues with their respective Rh blood types. (The ability to manage Time Travel intact is treated like a matter of genetics or blood type as well.)
- Dracula, thanks to Science Marches On. When the book was written, the concept of blood transfusions was radical, cutting-edge science, and the possibility of an allergic reaction to someone else's blood wasn't known. Thus, Lucy can get transfusions from four different men without anyone worrying about blood type compatibility. Since she's in the process of becoming a vampire, blood types may be irrelevant to her in a very easy retcon. Another easy Fan Wank is to claim that Lucy's an AB blood type.
- Everworld uses this trope correctly when the main characters have to give an emergency blood transfusion to Galahad. April volunteers because she's O-, the universal donor.
- Rare blood types always uncover parentage secrets on soap operas. All My Children used it a few years ago to reveal that Jack was Greenlee's father, though the rare blood type was never named. Much worse, One Life to Live back in the 80s had Tina find her lost son because they both had Blood Type G.
- On Dark Angel, Max, all of the other X5s, and most likely other transgenics as well, are specifically genetically programmed to have O- blood, so they could swap blood (and organs) on the battlefield. Also, the show makes the goof of a blood transfusion for Logan being difficult to find because he's AB-. Fortunately, universal donor Max was handy.
- The title character of Dexter has a rare blood type. It's shown in flashback that Dexter's foster father contacted Dexter's biological father when Dexter was injured and needed a blood transfusion.
- Good Times featured a rare blood type, U-, to facilitate a Who's on First? joke: "I have a very rare blood type, U Negative." "You positive?" "No, U Negative." And so forth.
- House both lampshades the first and subverts the second. The subversion is something we expect from a medical show, while the lampshading comes later as House solves a case based on a patient's blood type (and a conversation with Wilson): the patient had blood type A, but when he was given a blood transfusion, was given the wrong type. Nobody ever thought to ASK him what his blood type even was to begin with. Then again, the fact that doctors do not ask patients their blood type is Truth in Television. (In the episode, the patient's Lupus caused a blood test to give the wrong result.) Many people don't know, some think they know but are wrong, and very very few people know that more than the ABO/Rh factors even exist, much less what they have. And that's assuming the patient is conscious and coherent.
- In another episode, they play the trope straight. A woman in need of a liver transplant is apparently disadvantaged by having AB- blood. In fact, blood type would be the least of her worries.
- Lost features a scene in which Jack struggles to find a donor for Boone and, failing to find a match among the other survivors, reveals himself to be O- and performs the transfusion using his own blood. He actually got Charlie to ask nearly everyone in the camp their blood type but only 4 people knew.
- In "Journey to Babel", an episode of Star Trek: The Original Series, Ambassador Sarek requires open heart surgery which is hampered by his T- blood, noted as being rare, even for a Vulcan. Luckily, another person on board also had T- blood—Sarek's son, Spock, and even that had to be filtered because of Spocks human heritage.
- And since Vulcans have copper-based rather than Humans' iron-based blood, it's realistic that it would use a different blood type system.
- The Mash episode in real-time, where Hawkeye and company are racing against the clock to save a soldier who, according to Winchester, has "that elusive type".
- Normally averted on the show: All sorts of blood-types show up and they routinely run short of all of them.
- The writers adapted the trope to make its use accurate and believable for the time period. It's never said that the soldier can only take AB- blood; it's stated (by Potter) that AB- blood would be the best for him. In the 50s it was thought that the more blood the patient had lost, the more important it was to provide the exact blood type.
- They also had an episode about this. One wounded racist marine has a rare blood type and they tell him the only source is from a black soldier. They start applying make up to make him darker and darker until he believes he's turning black. After they tell him he learns some tolerance.
- In another episode a soldier is given the wrong blood and has a severe reaction. They gave the blood type listed on his dog tags - but they weren't his tags. He stole them from a buddy who was killed in the attack he was wounded in, because the buddy was just about to be sent home.
- The Pretender: Jarod and Kyle both had AB- blood, along with a young boy from one episode who was in dire need of a heart transplant. Guess where that went.
- (Sort of) averted on Angel where when a vampire has refrigerated blood on hand, it is usually "O-neg".
- Oz. When a prison guard is stabbed in the eyes and needs a blood transfusion, the only donor immediately available is inmate Ryan O'Reilly, who makes it a condition of his helping that his mentally-ill brother be moved into Em City with him.
- In Desperate Housewives, one of the characters began to suspect that another was their father because they both had AB- blood. Never mind that blood types don't actually work like this in real life (it's something to do with which factors you have and how they add together, he was far more likely to be A or B, and then positive simply because more people are positive and the positive genes are dominant, which is also why Rhesus negative women are more likely to have birth complications). It's also how Gabrielle ultimately learns that Juanita was Switched At Birth, which Carlos had tried to keep a secret from her.
- On Moonlight, Beth Turner has "AO-" blood, which is especially tasty to vampires. While technically a real blood group, AO is just a rather pedantic way of giving one of the two genetic possibilities for type A blood.
- The Hancock's Half Hour episode "The Blood Donor" is an iconic piece of British comedy. The Hancock character is nervous about giving blood at first but changes his mind when he discovers that his blood is AB- (although at one point the doctor tells him he is rhesus positive, causing him to remark "Rhesus? They're monkeys, aren't they?"). On returning home he pesters the hospital to make sure his blood is given to "the right sort of person", but then he injures himself, is rushed back to hospital and is given a transfusion of the blood he has just donated. Here We Go Again.
- In Forever Knight, they actually not only get the blood type info right, saying Schanke, who is AB+ , "can take anything but motor oil," while O- can only receive O-, it's involved in a plot point, too. The killer's mother had died from hepatitis contracted from a blood transfusion, which slipped through the screening process; he was taking out only O- donors who could have been the source.
- On Charmed, Piper has AB negative blood as does Andy. This is shown in the episode "The Wendigo". The Wendigo also attacks people with the AB negative blood type.
Piper: Yeah, I'm fine. If I pass out and I need a transfusion, I'm AB negative. It's very rare. It could be a problem.
Andy: Uh, I was just thinking how I'm probably not the best cop to be on this stakeout with, seeing as how I'm, uh, AB negative.
Andy: Maybe. I've just gone over the coroners reports from Chicago, New Orleans, and now local. It turns out all the victims were AB negative.
- A third season episode of Chuck features Casey having to donate his AB- blood to save the life of a man he'd been trying to kill off and on for years (well, Chuck 'stole' it, but whatever).
- In the last season of Queer as Folk, after the bombing in Babylon, Michael has been seriously hurt and taken to the hospital. The ER doctor says he needs a blood tranfusion, but he's AB negative and they are short on his type. Brian answers he's O negative, universal donor and wants them to take his blood. But they won't take it because he's gay and they are considered too high of a risk for HIV. Brian then goes berserk, but Ben tells him he couln't give his blood anyway because he had cancer. This is a reference to the Ban On Blood Donations From Gay Men in the USA implemented in 1985, and despite what the show says the policy isn't as set-in-stone as many media outlets make it seem. Doctors at hospitals are desperate for any compatible blood type in a pinch, and in real life they more than likely wouldn't turn Brian away if he were on the scene. It's only at blood drives that they screen for gay men (which is still horrible, but my original point stands). It was all just a convenient excuse for an Anviliciously dramatic take on a real gay issue.
- Comes up twice on The A-Team. The first time, B.A. needs a blood transfusion, type AB Negative. The only other member of the team with this blood type is Murdock. The second time, Murdock needs a transfusion. Guess.
- Gossip Girl: Dan and Rufus Humphrey are both AB+. Milo, Georgina's and Dan's "son" is 0-.
- In Terminator: The Sarah Connor Chronicles, they mentioned that Sarah had O- blood but John had AB- blood; this would mean that she couldn't possibly be his mother, barring vanishingly rare situations like mutation or Bombay blood type. Note that Sarah being unable to give blood to the AB- Derek Reese despite being a universal donor could be correct, since she's giving whole blood containing plasma, not just blood cells, and compatibility for plasma is reversed compared to blood cells—someone with type O is the least useful donor because their plasma could contain antibodies against non-O blood types.
- This is confirmed (again) from Robert A. Heinlein's I Will Fear No Evil where Johann explains how he loved his son more than life itself, even though he knew that his son's blood type was O and his was AB, he has to explain he knew from birth that his son wasn't his because the blood typing was incompatible.
- Another blend of this with Did Not Do the Research appeared on Law and Order SVU, when a comatose woman's mysterious pregnancy is under investigation. Her blood type is A and the fetus's is AB, so the investigators conclude that its father must be type B ... even though a type AB father would also have a 50/50 chance of passing the B trait on to his child. Particularly deserving of a You Fail Genetics Forever is Wong, who agrees that the father's type must be B despite his own medical training.
- And again on SVU, they assert that two type A parents must have a type A child.
- True Blood. The (sorta) titular drink has each blood type as a separate flavor, and vampires have preferences on their favorite. Newbie vamp Jessica drinks a cocktail of several different types to get used to the taste.
- One episode of Dads Army was based around Pike being called up to join the regular army. The platoon can't get him out of it, so they hold a fish and chip supper to say goodbye to him - after which Pike announces that he was excused from joining the army because he has a very rare blood type, but didn't want to tell anyone until after the fish and chips.
- The season-two finale of Monk featured a victim whose blood group was "AB-negative with a D-antigen--the rarest blood-type in the world!" It is indeed rare; in fact, it doesn't exist. This turned out to be why he was murdered—he was a death row inmate about to be executed, with his blood going to a local philanthropist in need of an operation. A prison employee had a grudge against the philanthropist and couldn't let that happen, so they poisoned the prisoner's last meal, making the blood worthless
- Psych actually did the research in a recent episode. A man needed O negative donations of course Lassiter is the needed bloodtype.
- In a variant on CSI, a power outage shuts down the lab's equipment, and the investigators must resort to old-school ABO typing of blood evidence. Greg remarks that he's got clumping in his Type O sample; this is an error, as Type O is distinguished as such by its failure to clump when exposed to anti-A or anti-B serum. (It could've been O-positive and clumped in anti-Rh serum, but Rh-typing wasn't otherwise mentioned.)
- German singer Udo Lindenberg once made the song "0 rhesus negativ" where he meets a vampire, but is spared because the vampire can't stand that special blood type.
- In the middle school musical Dracula, Baby Dracula offers to do anything in his power to help Lucy. He is asked if he's type B (Lucy's type) or O - the universal donor. He replies that he's type AB - the universal receiver.
- Shadow Hearts: Covenant has a door in one dungeon that will only open if a person with AB blood tries to open it; this was done by its builder to ensure her apprentice, the party member Lucia, wouldn't get into things she shouldn't. Only one member of your party can open it, leading to a brief puzzle to determine which of your party members is AB. Oddly enough, it isn't Yuri (type A) or Karin (also type A), the main characters—it's Gepetto. Joachim is type O and Lucia is type B.
- Toko in Kara no Shoujo is of the Bombay blood group which means that she can't get a blood transfusion after getting hit by a truck.
- In Darths and Droids, Qui-Gon's player has his character's blood type written on his character sheet. It's O- making him a universal donor, however he actually wanted AB+ to make the character more capable of receiving medical treatment, but didn't know that there was a difference, and the type he picked would only be useful if he just needed blood plasma. Pete brings up that a universal recipient would be preferable, but he's also the Munchkin of the group.
- King of the Hill sees Peggy bragging to neighbour Minh about how she has blood of type AB- and giving this trope its name.
- The Simpsons second season episode "Blood Feud," Mr. Burns needs a OO- transplant, and Bart is the only person in town with the same blood type. He uses it as a bargaining chip. While it is correctly described as rare, its rarity is greatly exaggerated.
- They make a point of it being double-O negative, not just O-neg. It may be a case of fictionalized blood type.
- In South Park, it is revealed that Kyle and Cartman are the only two people in town with AB- blood... leading to some problems when Kyle needs a kidney transplant and Cartman won't let him have it.
- This is strange since much later in "Cartman Sucks" Butters reveals he has type O blood, so he should be compatible with Kyle too, but is never asked.
- An episode of Courage the Cowardly Dog has a government agency capture Muriel because she was one of the three or so people on the planet with the blood type "ABXYZ."
- The plot of the Batman the Animated Series move Sub Zero involves Mr. Freeze kidnapping Barbara Gordon because she shares the AB- blood type with his wife. Barbara even brings up that he could use any negative blood for a blood transfusion, but it turns out that he needs more than just her blood. Truth in Television in that organ transplants are ideally done between people of the same blood type to reduce the risk of rejection, and Mr. Freeze is obsessive enough over getting his wife back that he'd try to be as exact as possible.
- In Young Justice, young Garfield gets into an accident, and needs a transfusion of type O blood, of which the isolated farm's supplies were just destroyed. Nobody on site has O-blood, except Miss Martian, who can transform her cells. This will probably give the character transformation powers, making him Beast Boy.
- Bombay Type blood is an extremely rare blood type that cannot accept any Rh factored blood, positive or negative. So while they test as type O negative due to a lack of Rh antigens, they will have a hemolytic reaction if given O negative (which is otherwise considered the universal donor for blood, or AB positive plasma) and must be given Bombay blood. For this reason when a blood bank receives a Bombay donation, they never discard it as they do with other blood types after a certain period or expiration date. It's named after the city in which it was discovered, and people who have it are mostly concentrated in that region of India (and even there they're a minority), and practically nowhere else in the world.
- For the record, type O is recessive, and Sarah is therefore by necessity homozygous for O. Johny could be AO (type A) or BO (type B), but type AB is not possible