The best way to tell is to u003cstrongu003etaste it.u003c/strongu003e  Sprinkle a little onto a spoon, and dip a wet finger into it.  If the gingeru003cstrongu003e taste is not prominent, or hardly there, its best to discard it u003c/strongu003eand buy a new one.  Using old ground ginger in a recipe in higher quantities won’t bring it back to life if you can barely taste the ginger flavour in the first place.