# What is the difference between blood types? **URL:** \ **Category:** Factual Questions\ **Created:** [January 17, 2000, 3:35am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294 "2000-01-17T03:35:00Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Llardball](https://avatars.discourse-cdn.com/v4/letter/l/f6c823/32.png) [@Llardball](https://boards.straightdope.com/u/Llardball)\ **Post date:** [January 17, 2000, 3:35am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/1 "2000-01-17T03:35:00Z")
I’m sure this question was asked at some point, but I never saw it nor did I see the answer. Can anyone fill me in? I’m talking about the difference between types such as Type A, O positive, etc. * * * I realize I’m generalizing here, but as in most cases, I don’t care. -Dave Barry ---
**Author:** ![Alphagene](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@Alphagene](https://boards.straightdope.com/u/Alphagene)\ **Post date:** [January 17, 2000, 4:07am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/2 "2000-01-17T04:07:00Z")
From [this site](http://my.webmd.com/content/dmk/dmk_article_1456797): > [@](#): > > A and B represent proteins that are found on the surface of blood cells. O represents the absence of either of these proteins. Since a person receives two genes for blood groups (one from each parent), one can fall into four groups: A, representing either two A genes (AA) or one A gene and an O gene for which there is no protein produced; B, similar to A; O, if one receives O genes from both the parents; or AB. * * * We gladly devour those who would subdue us. ---
**Author:** ![Alphagene](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@Alphagene](https://boards.straightdope.com/u/Alphagene)\ **Post date:** [January 17, 2000, 4:09am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/3 "2000-01-17T04:09:00Z")
Oh yeah, from the same site: > [@](#): > > The Rhesus system defines two blood types: blood in which the Rh factor is present (Rhesus positive, or Rh+), and that in which it is not (Rhesus negative, or Rh-). * * * We gladly devour those who would subdue us. ---
**Author:** ![Ringo](https://avatars.discourse-cdn.com/v4/letter/r/779978/32.png) [@Ringo](https://boards.straightdope.com/u/Ringo)\ **Post date:** [January 17, 2000, 4:23am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/4 "2000-01-17T04:23:00Z")
Alpha, Just to make sure I understood: > [@](#): > > …or one A gene and an O gene for which there is no protein produced… produces O? And O as well if one B gene and an O gene? ---
**Author:** ![Ringo](https://avatars.discourse-cdn.com/v4/letter/r/779978/32.png) [@Ringo](https://boards.straightdope.com/u/Ringo)\ **Post date:** [January 17, 2000, 4:25am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/5 "2000-01-17T04:25:00Z")
Forget it, Alpha, I went to the site you linked and read (which I should’ve done before posting - sorry). ---
**Author:** ![Boris\_B](https://avatars.discourse-cdn.com/v4/letter/b/fbc32d/32.png) [@Boris\_B](https://boards.straightdope.com/u/Boris_B)\ **Post date:** [January 17, 2000, 5:54am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/6 "2000-01-17T05:54:00Z")
I think it might be useful to add that the various blood types are sometimes but not always okay for donation to one another. Basically, you can safely receive blood as long as it doesn’t have a “letter” that isn’t in your blood naturally. Since type-O doesn’t have either “letter”, everyone can receive blood from a type-O donor. Type-As can donate only to other type-As and type-ABs. Type-ABs can receive from anybody at all, those lucky ducks. Don’t know how the Rhesus factor fits in though … is type-O positive the universal donor, or type-O negative, or both? ---
**Author:** ![GuanoLad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guanolad/32/42_2.png) [@GuanoLad](https://boards.straightdope.com/u/GuanoLad)\ **Post date:** [January 17, 2000, 7:15am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/7 "2000-01-17T07:15:00Z")
> [@](#): > > Type-ABs can receive from anybody at all, those lucky ducks. Woohoo! I’m AB+ !!! * * * **-PIGEONMAN-** Returns! [The Legend Of PigeonMan](http://www.hotkey.net.au/~guanolad/pigeonman/) - **By Popular Demand!** Enjoy, enjoy! ---
**Author:** ![RickG](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rickg/32/5174_2.png) [@RickG](https://boards.straightdope.com/u/RickG)\ **Post date:** [January 17, 2000, 7:23am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/8 "2000-01-17T07:23:00Z")
O-negative is the universal donor. O+ can donate only to other Rh-positive people. Rick (Proudly pumping O- blood through my own veins for over 35 years!) ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [January 17, 2000, 8:49am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/9 "2000-01-17T08:49:00Z")
Rh factor was found when serum from Rhesus monkeys was added to blood from humans, and it was noted that some blood cells “agglutinated” when exposed to certain elements of the Rhesus blood. The “Rh factor” indicates whether your blood would agglutinate (+) or would not (-). The precise chemistry which causes this, was not known at the time the identification was made. The correlation with severe reactions was known, and the factor was adopted as a useful test to eliminate probable bad matches. It was soon also noted that many handicapped children who were Rh+ were second children born to women who were Rh-. Further investigation revealed that all such children had fathers who were Rh+, as well. (I might have that reversed, but I think it is right.) Eventually it was learned how to prevent the harm done to both mother and child in that case, with medications. ## **\

Tris\** Thou shalt not answer questionnaires Or quizzes upon world affairs, Nor with compliance Take any test. Thou shalt not sit with statisticians nor commit A social science. – \*\*W H Auden \*\* ---

**Author:** ![Llardball](https://avatars.discourse-cdn.com/v4/letter/l/f6c823/32.png) [@Llardball](https://boards.straightdope.com/u/Llardball)\ **Post date:** [January 17, 2000, 4:20pm UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/10 "2000-01-17T16:20:00Z")
How do you go about finding out your blood type? Is it on record with your doctor? Also, why would you want to disable smilies on a post? Just a side note. ---
**Author:** ![Bricker](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@Bricker](https://boards.straightdope.com/u/Bricker)\ **Post date:** [January 17, 2000, 4:26pm UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/11 "2000-01-17T16:26:00Z")
> [@](#): > > Originally posted by RickG: > \*\*O-negative is the universal donor. O+ can donate only to other Rh-positive people. > > Rick (Proudly pumping O- blood through my own veins for over 35 years!) \*\* I’m A+. As I read this, that means I could receive only O- or O+, yes? - Rick ---
**Author:** ![Boris\_B](https://avatars.discourse-cdn.com/v4/letter/b/fbc32d/32.png) [@Boris\_B](https://boards.straightdope.com/u/Boris_B)\ **Post date:** [January 17, 2000, 4:49pm UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/12 "2000-01-17T16:49:00Z")
You could also receive A positive blood, and if I’m reading this correctly, A negative blood as well. Keep in mind that the doning limitations are for _whole blood only_; I think anybody can receive plasma from anybody, since they take all the other stuff out in a centrifuge. So if you are an AB positive person, and you are feeling socially responsible, it would probably better to donate plasma since your whole blood wouldn’t be especially useful. ---
**Author:** ![tanstaafl](https://avatars.discourse-cdn.com/v4/letter/t/ba8739/32.png) [@tanstaafl](https://boards.straightdope.com/u/tanstaafl)\ **Post date:** [January 17, 2000, 5:37pm UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/13 "2000-01-17T17:37:00Z")
The people at the Red Cross explained it to me by saying “Think of blood types as being added together.” O + O = O, O + A = A, O + B = B, O + AB = AB, A + A = A, A + AB = AB, B + B = B, B + AB = AB and AB + AB = AB. For Rh factors ‘-’ + ‘-’ = ‘-’, ‘-’ + ‘+’ = ‘+’ and ‘+’ + ‘+’ = ‘+’. When receiving blood, you can accept any blood type as long as it and your own blood “add up” to the type you already have. For example, if you are B+ you can receive O- because B+ + O- = B+. You cannot receive A- because B+ + A- = AB+ (which isn’t you). ## I’m A- which is one of the ones they seem to like getting. My mother is O-; true universal donor but can only receive O- blood. “Drink your coffee! Remember, there are people sleeping in China.” Dennis Matheson — [dennis@mountaindiver.com](mailto:dennis@mountaindiver.com) Hike, Dive, Ski, Climb — [www.mountaindiver.com](http://www.mountaindiver.com) ---
**Author:** ![torq](https://avatars.discourse-cdn.com/v4/letter/t/dfb087/32.png) [@torq](https://boards.straightdope.com/u/torq)\ **Post date:** [January 17, 2000, 8:58pm UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/14 "2000-01-17T20:58:00Z")
I know, casually, someone who works for the Red Cross. From various things he’s said I’ve pieced together that while theoretically you could just give O- blood to everyone, in practice they seem to strongly prefer using actual matches. Whether this is to preserve O- for people who really NEED that and nothing else, or if there’s some other reason, I don’t know. One way to find out what type you are, assuming you’re qualified to be a donor, is to donate blood. They’ll type it and let you know when they send you your donor card. That’s how I know mine (A+). ---
**Author:** ![Kat](https://avatars.discourse-cdn.com/v4/letter/k/b19c9b/32.png) [@Kat](https://boards.straightdope.com/u/Kat)\ **Post date:** [January 18, 2000, 1:46am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-blood-types/6294/15 "2000-01-18T01:46:00Z")
> [@](#): > > Originally posted by Llardball: > **How do you go about finding out your blood type? Is it on record with your doctor?** Yes, it’s probably in your medical records. Some people may have found out in other ways. For example, I always remember that I have type B, because I had to do the “stab yourself in the finger and test your blood type” experiment in HS biology. (Not an easy thing for a needle-phobic person to do.)