US: Many people do not know theirs. It isn't something that is used unless you need medical attention. (I know mine because I donate blood.)

Thank you for letting me know in detail, Bill. I feel something strange :)

I also am from the US, and I am older than 60 years old. I learned what my blood type was because of a class experiment when I studied biology in school. Every student in the class drew their own blood and tested it to determine their own blood type. My test was confirmed by the Red Cross about 3 years later, when I donated blood for the first time and then they sent me a blood donor ID card that stated my blood type. While I was growing up it was not common for doctors to test your blood type and tell you what it is unless there was a specific medical need to do that. As Hilary said, most people in the US learn their blood type because they need to have a blood transfusion, because they donate blood, or because they are pregnant and the doctors want to know whether the mother is Rh- and the baby is Rh+.

Thank you, everyone :) What a surprise ...it was true! We usually find it out (A,B,O,AB) by a blood test when we were born in Japan.

I grew up north of the Golden Gate Bridge, just above San Francisco, California, USA, I am over 60 years old, and since I have never had surgery, donated blood, needed a blood transfusion, or had children, I do not know my blood type.