Blood in urine. Here is another common symptom of kidney illness. Your kidney is closely connected to the urinary system, and in case a kidney is ill, the urinary system suffers too. The most obvious symptom would be a presence of blood in your urine. This is one of the most dangerous symptoms, and you should go to the hospital as soon as you can. Sometimes there are no obvious blood signs, but a different color of your urine. You should start worrying in case it is too dark, red or pink.