Myoglobin - plasma or serum

5 mL blood in lithium heparin or plain tube.

< 70 µg/L.

Increased levels are found in any condition causing muscle cell damage including myocardial infarction.

Myoglobin levels rise rapidly following myocardial infarction, peaking by about 90 minutes, but the protein is cleared rapidly by the kidneys.

This test is non-specific and, if myocardial infarction is suspected, any raised value should be followed by a troponin assay.

Levels are also increased in patients with rhabdomyolysis but urine myoglobin suffices to confirm myoglobinuria and is the preferred test.