Fast heartbeat and dizziness may be caused by emotional excitement, arrhythmia, hyperthyroidism, hypoglycemia, anemia and other reasons. 1. Emotional excitement: the heart muscle is excited and oxygen consumption increases during physical situations such as strenuous exercise, emotional excitement and stress, so this symptom will appear. 2. Arrhythmia: atrial fibrillation, premature beats, ventricular tachycardia and other diseases when the heart’s excitatory tissue, conduction block and other dysfunctions, resulting in the disappearance of the heart’s normal rhythm, accelerated heart rate, reduced per-beat output, insufficient blood supply to the brain tissue, so the symptoms. 3. Hyperthyroidism: hyperthyroidism secretes a large amount of thyroid hormone, which leads to hypermetabolism of the heart, accelerated heart rate, and elevated blood pressure, so this symptom will appear. 4. Hypoglycemia: When blood sugar is too low, the lack of energy supply to the tissues and reflex excitation of the sympathetic nerves, resulting in increased heart rate and lack of oxygen to the brain cells. 5. Anemia: Insufficient red blood cells and hemoglobin lead to limited blood and oxygen supply to the tissues, so this symptom will appear. Fast heartbeat and dizziness may be related to a variety of factors, it is recommended to consult a doctor for a clear diagnosis.