Diarrhea may cause myocarditis, so cardiac enzymes need to be checked for confirmation to avoid missing the diagnosis. Bacteria and viruses can cause diarrhea. Bacteria that can cause diarrhea include streptococcus bacteria, and viruses include influenza virus, norovirus, and rotavirus. Severe diarrhea can lead to water loss, increased blood levels, slowed metabolism, and electrolyte disorders, increasing the burden on the heart and damage to the heart muscle. Cardiac enzymes are often used as the most sensitive and specific indicator of myocardial damage. Rotaviruses and influenza viruses can cause myocarditis, which may be contracted through diarrhea, and may present with symptoms such as diarrhea that is not severe, but with depression. In addition, myocarditis can damage cardiomyocytes, so it is necessary to check whether cardiac enzymes have caused myocarditis to avoid missing the diagnosis. If similar symptoms occur, early and standardized treatment is recommended to reduce the adverse effects of the disease.