A CK (Creatine Kinase) or CPK (Creatine Phosphokinase) test measures this enzyme in your blood, which indicates damage to muscles (skeletal, heart, brain) as the enzyme leaks out from injured tissue, helping diagnose conditions like heart attacks, muscle diseases (muscular dystrophy, rhabdomyolysis), or brain injuries. It’s a simple blood test, often ordered with symptoms like muscle pain or weakness, and different CK types (CK-MM, CK-MB, CK-BB) help pinpoint the source of the damage