What are signs to tell if kidneys are failing, or have failed???

No urine: The ultimate way to tell, (and then it's probably too late ), is no urine output. Before that happens you could have either lower output of urine than normal, or higher output than normal. You might also notice swelling of your body. However, those symptoms can be caused by things other than crappy kudneys, so don't assume. You can also get blood tests that check kidney function specifically....