Blood type compatibility.

Here is a simple table about blood compatibility

Guess a+ and a- are useless...

You forgot blood type A.

Being O-neg makes you a universal donor, but you can only ever receive O-neg if needed.

I donated once, just once and that was for my own pre surgery standby supply if needed. I’m O- and I get a call from them monthly begging me to donate. Whoever thought it was a good idea to list me as a donor when I never did any such thing has some explaining to do. It’s like a credit report. To change anything on it is close to impossible and you never do get the answers on how and why it happened!

Because O-negative blood lacks A, B, and D antigens, which can trigger an immune response in recipients who aren't a match, O-negative blood is sometimes called "universal donor" blood. It can be transfused to almost any blood type, making it critical for emergency medical care

We used to hear that O+ was universal donor

I bookmarked this. (I'm an EMT)

A+ ?

Where’s the A examples?