Heart rate, which is measured as the number of times your heart beats per minute (bpm), can vary depending on the level of activity you are engaged in and how much oxygen your body needs. When determining your regular heart rate, doctors take your 'resting heart rate'. The pulse is checked only after you have been resting for at least 10 minutes. The normal ranges for resting heart rate are 60 - 100 bpm for children over 10 and adults or 40 - 60 bpm for athletes.
An unusually high heart rate that hasn't been documented previously may be due to anxiety, dehydration or infection. A consistently high heart rate is called sinus tachycardia. For some, tachycardia causes no other symptoms or complications. In other cases, a high pulse rate can cause dizziness, shortness of breath, lightheadedness, palpitations, chest pain and fainting due to insufficient oxygen reaching your organs. Factors that can contribute to tachycardia include: congenital abnormalities, damage to the heart tissues due to disease or infection, drinking too much alcohol or caffeine, drug abuse or smoking, electrolyte imbalance, high blood pressure, hyperthyroidism, and medication side effects.
If you have a high pulse rate, discuss your symptoms with your doctor. Treatment will depend on the cause, the severity and the gravity of the issue; some cases can be treated with habit changes and medications, but others may require surgical intervention.