After quitting smoking, the heart rate drops from 100 beats/min to 70 beats/min. The normal adult heart rate range is 60 to 100 beats per minute in quiet, awake conditions, with slower rates in the elderly, slightly faster rates in women, and faster rates in children. Where the adult heart rate more than 100 beats / min is called tachycardia. A heart rate of less than 60 beats per minute is called bradycardia. A heart rate of 70 beats per minute is within the normal range. In some people, smoking for a long time may cause the heart rate to increase. This is because the nicotine in smoke and other harmful substances stimulate the sympathetic nervous system to release a lot of catecholamines, which stimulate the sinus node to send electrical impulses to speed up the frequency of the heart can make the heart beat faster. Therefore, it is normal for the heart rate to decrease after quitting smoking. Smoking has many harmful effects on the body, and it is normal for the heart rate to slow down after quitting smoking. If your heart rate slows down and you feel unwell, it is recommended that you go to the hospital in a timely manner and be examined under the guidance and advice of a professional doctor to rule out possible underlying diseases.