CREATINE KINASE THIS TEST MEASURES THE AMOUNT OF CREATINE KINASE IN BLOOD.CK IS USED TO EVALUATE TISSUE DAMAGE, PARTICULARLY MUSCLE TISSUE, OR TO DETECT INFLAMMATION OF THE MUSCLES (MYOSITIS) AND SERIOUS MUSCLE DAMAGE AND/OR TO DIAGNOSE “RHABDOMYOLYSIS” IF A PERSON HAS SIGNS AND SYMPTOMS, SUCH AS MUSCLE WEAKNESS, MUSCLE ACHES, AND DARK URINE.THE URINE MAY BE DARK BECAUSE OF THE PRESENCE OF MYOGLOBIN, ANOTHER SUBSTANCE RELEASED BY DAMAGED MUSCLES THAT CAN BE HARMFUL TO THE KIDNEYS.