A heart rate of more than 100 beats per minute in adults, a condition called tachycardia, is considered fast according to The American Heart Association. However, what is considered fast depends on the age and physical condition of an individual.
The normal range for heart rate is 60 to 100 beats per minute. A fast heart rate is normal during exercise or any kind of physical activity. The increased heart rate helps the heart pump more blood and provide adequate oxygen to all areas of the body. Fear, anxiety and stress also increase the heart rate. A fast heart rate may also be a side effect of certain medications, according to Chemocare.com.