A heart rate of 45 beats per minute while sleeping is not normal, as the normal heart rate is 60-100 beats per minute. During sleep, the human heart rate will be slightly lower than the normal heart rate, but it should not be lower than 55 beats per minute, so 45 beats per minute during sleep needs to be checked in the hospital. The tests include electrocardiogram, 24-hour ambulatory ECG, cardiac ultrasound, coronary CT, nuclear myocardial imaging and so on. These tests can identify the causes of slow heart rate, such as anemia, malnutrition, malignant tumors, and even coronary heart disease and heart valve disease. Once the cause is identified, active treatment is needed to bring the heart rate back to normal.