DayZ field wiki · Medical
Blood types
A letter before a bag
Short answer
Blood bags want a match. Saline does not. Tests exist.
Also: blood type · blood group
How it works
DayZ models blood groups. Wrong bags are a story with a known ending. Exact compatibility charts stay empty rather than wrong.
What to do
Test. Label. Prefer saline if you don't know. See blood-test.
Don't
Don't guess Kane's type as a bit.