Alpha-hydroxybutyrate dehydrogenase is an enzyme in the cardiac enzyme profile, equivalent to an active enzyme in lactate dehydrogenase, found mainly in cardiac muscle cells, but also in the kidney. This enzyme is clinically elevated and is clinically relevant. It is increased in chronic myocarditis and in heart attacks that lead to myocardial damage. Hemolytic diseases can also cause an increase in this enzyme. It is important to exclude that the increase is caused by improper operation of nurses, such as in vitro hemolysis caused by improper operation during blood sampling. It is also important to rule out the presence of neoplastic diseases, such as leukemia, which may also increase.