The CK (Creatine Kinase) test measures levels of an enzyme primarily found in skeletal muscles, the heart, and the brain. This enzyme plays a key role in cellular energy production, and elevated levels in the blood typically indicate damage to CK-containing tissues. High CK-MM levels are often linked to skeletal muscle injury (e.g., rhabdomyolysis, trauma, intense exercise, or muscular dystrophies), while CK-MB is primarily associated with cardiac damage (e.g., myocardial infarction), though troponin is now preferred as a more precise cardiac injury marker. CK-BB is rarely measured and may rise in brain injuries or certain tumors. This test is used to diagnose muscle diseases, monitor drug side effects (e.g., statins), or assess acute injuries. Results must be interpreted alongside clinical symptoms, medical history, and other tests, as non-pathological factors like strenuous exercise can temporarily elevate CK levels.