how to transition height differences between rooms

[jetman1]

I have a problem. The floor to the kitchen is 2" above the floor to the back room.  How do I make a threshold that will prevent injury stepping up or down?

The floors heights cannot be changed from contractor mistakes.

Tapering the threshold would be dangerous, and way to wide.  I could go with a flat threshold, and step down 2".  How wide would I have to make that happen?