Type of test Blood
Normal findings
< 90 mcg/L or < 90 mcg/L (SI units)
Test explanation and related physiology
Myoglobin is an oxygen-binding protein found in cardiac and skeletal muscle. Measurement of myoglobin provides an early index of damage to the myocardium in myocardial infarction or reinfarction. Increased levels, which indicate cardiac muscle injury or death, occur in about 3 hours. Although this test is more sensitive than creatine phosphokinase (CPK) isoenzymes, it is not as specific. The benefit of myoglobin over CPK-MB is that it may become elevated earlier in some patients.
Disease or trauma of the skeletal muscle also causes elevations in myoglobin. Because myoglobin is excreted in the urine and is nephrotoxic, urine levels must be monitored in patients with high levels. Myoglobin may turn the urine red.
Interfering factors
• Increased myoglobin levels can occur after IM injections.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: red
Abnormal findings
Increased levels
- Myocardial infarction
- Skeletal muscle inflammation (myositis)
- Malignant hyperthermia
- Muscular dystrophy
- Skeletal muscle ischemia
- Skeletal muscle trauma
- Rhabdomyolysis
Decreased levels
- Polymyositis
