The causes of high heart rate include endocrine metabolic diseases, heart diseases, respiratory diseases, anemia, emotional changes, etc. 1. Among the endocrine diseases, hyperthyroidism is the most likely to cause fast heart rate because thyroxine increases in the body during hyperthyroidism, leading to an increase in heart rate. 2. Many heart diseases can cause fast heart rate, such as heart failure, atrial fibrillation, rapid atrial arrhythmia, and frequent premature beats. 3. Chronic lung diseases are also prone to fast heart rate, such as emphysema and pulmonary embolism, which can lead to lack of oxygen in the body, and lack of oxygen can cause fast heart rate. 4. Anemia is also associated with fast heart rate. 5. Fast heart rate can also occur when there are emotional changes, such as excitement, excitement, and when staying up late.