Low hemoglobin affects the heart. Low hemoglobin may aggravate the burden on the heart, and long-term low hemoglobin may lead to heart failure. Low hemoglobin indicates that the patient is in a state of anemia, the patient’s ability to transport oxygen decreases, and various tissues and organs in the body will experience ischemia and hypoxia. In this case, the organism will overload its compensatory work to increase the output of the heart in order to maintain the blood supply and oxygen supply of the vital organs, so as to maintain the normal functioning of the organism. If prolonged low hemoglobin results in sustained cardiac overload compensation, it can lead to enlargement of the heart as well as reduced contractility. Severe hemoglobin deficiency may result in ischemia of the heart, acute angina and myocardial infarction. When low hemoglobin is detected, the cause of the condition should be identified and hospitalization is recommended.