The heart rate, also called the pulse, is the number of times the heartbeats per minute (BPM).
According to the American Heart Association, a normal resting heart rate is between 60 (beats per minute) and 100 (beats per minute) for people 15 years and older.
Heart rate can be dangerous if it is too high (the medical term for a fast heart rate is tachycardia). In general, a fast heart rate for adults is over 100 beats per minute (bpm).
Common everyday causes of a fast heartbeat that may not always be a cause for concern may include:
- Vigorous exercise
- Stress
- Fear
- Anxiety or panic attacks
- Low blood sugar (hypoglycemia)
- Low blood pressure (hypotension)
- Fever
- Anemia
- Dehydration
- Pregnancy
- Menstruation
- Too much alcohol, caffeine, or nicotine
- Illegal drugs such as ecstasy, methamphetamines, or cocaine
Serious conditions that can cause a fast heartbeat include:
- Heart failure
- A past heart attack
- Coronary artery disease (CAD)
- Problems with the heart’s valves or muscles
- Irregular heartbeats (arrhythmias), including atrial fibrillation (AFib)
Call 911 or get to a hospital’s emergency department (do not drive yourself) if you have an unusually fast heart rate accompanied by symptoms such as:
- Chest pain or tightness
- Shortness of breath
- Dizziness
- Lightheadedness
- Fainting
- Fatigue
- Exercise intolerance
What Is a Normal Heart Rate?
Normal resting heart rates by age are as follows:
| Age range | Heart Rate (beats per minute, or BPM) |
|---|---|
| Newborn | 100-160 |
| 0-5 months | 90-150 |
| 6-12 months | 80-140 |
| 1-3 years | 80-130 |
| 3-5 years | 80-120 |
| 6-10 years | 70-110 |
| 11-14 years | 60-105 |
| 15 years and older | 60-100 |
How Do I Calculate Maximum Heart Rate?
- To estimate the maximum target heart rate during exercise, subtract your age from 220. For example, for a person who is 50 years, the estimated maximum age-related heart rate would be calculated as 220 – 50 years = 170 bpm.
- For moderate-intensity physical activity, the target heart rate should be between 64% and 76% of the maximum heart rate. For that same 50-year-old, that would mean their target heart rate for moderate-intensity physical activity should be between 109 to 129 bpm.
- The target heart rate for vigorous-intensity physical activity should be between 77% and 93% of the maximum heart rate. That means a target of 131 to 158 bpm for that same 50-year-old.
From 
https://www.heart.org/
https://emedicine.medscape.com/article/2172054-overview#a2
https://www.cdc.gov/physicalactivity/basics/measuring/heartrate.htm
https://healthcare.utah.edu/cardiovascular/conditions/racing-heartbeat.php