What will happen if you inject someone elses blood in you that's not the same blood type?

Injecting someone else's blood that is not the same blood type can lead to a severe immune reaction, known as a transfusion reaction. The recipient's immune system may recognize the foreign blood cells as a threat and attack them, which can cause symptoms like fever, chills, and potentially serious complications such as kidney failure, shock, or even death. It's crucial to match blood types before any transfusion to prevent these dangerous outcomes.