Sinus tachycardia of 120 beats/min depends on different situations to decide whether it is serious or not. For example, physiological, due to drinking a lot of tea, alcohol or coffee, staying up late or strenuous exercise, can reach sinus tachycardia of 120 beats/min. This is not a serious condition, and the heart rate can be normalized with adequate rest and emotional stability. Other non-cardiogenic sinus tachycardia of 120 beats/min is hyperthyroidism or anemia or fever, such as hyperthyroidism, and some people are seen with sinus tachycardia, which requires active control of the hyperthyroidism. Some patients are anemic and have a particularly low hematocrit, reaching a sinus tachycardia of 120 beats/min. In this case, the sinus tachycardia can be terminated by actively looking for the cause of the anemia and correcting it. In some patients with fever, the body temperature reaches 39-40℃ and the heart rate is also fast. There are also patients with gastrointestinal hemorrhage and patients in shock who have increased heart rates, which will be relieved by actively correcting the shock, which is more serious and requires urgent medical attention. There are also some cardiogenic diseases, such as myocarditis, pericardial effusion, or various kinds of heart failure, where the patient’s heart rate reaches 120 beats per minute is more critical, so it is necessary to consult a hospital for treatment at the first time.