Myoglobin is a small, oxygen-binding protein found in heart and skeletal muscles. It traps oxygen within muscle cells, allowing the cells to produce the energy required for muscular contraction. When heart or skeletal muscle is injured, myoglobin is released into the blood. Elevated levels can be measured within a few hours following an injury.
Myoglobin is filtered from the blood by the kidneys and is released into the urine. Large quantities of myoglobin are toxic to the kidneys. If significant amounts of myoglobin are released into the bloodstream, which can happen after severe trauma or muscle injuries, the excess myoglobin may cause damage to the kidneys and eventually result in kidney failure. Measurement of myoglobin in urine helps to detect this condition.