A hemoglobin of less than 90 is considered moderate anemia, which may lead to a decrease in the patient’s physical ability and may cause a series of symptoms such as dizziness, fatigue, pale skin, and may also induce anemic heart disease. Hemoglobin is a special protein that transports oxygen within the red blood cells, and its level is related to the oxygen-carrying capacity of the body. Therefore, patients with a hemoglobin of less than 90 may experience shortness of breath and difficulty breathing with a little exercise. In addition, due to insufficient supply of oxygen to the brain, symptoms such as headache, dizziness, blurred vision, memory loss, and lack of concentration may also occur. If the patient has had poor cardiac function in the past, prolonged hemoglobin below 90 may further deteriorate cardiac function, which is caused by insufficient supply of oxygen to the body due to anemia, causing the heart to do extra work to compensate for the supply of oxygen. If the hemoglobin is below 90 and it is clear that the anemia is moderate, please consult the doctor as soon as possible to identify the cause and actively correct the anemia.