The heart rate is the number of times the heartbeats per minute (BPM). According to the American Heart Association, a normal adult resting heart rate is between 60 beats per minute (BPM) and 100 BPM for people 15 years and older.
A resting heart rate below 60 BPM is considered bradycardia, which is the medical term for a heart rate that is too slow. However, what’s considered too slow can depend on a person’s age and physical condition.
- Elderly people and those who take medications such as beta-blockers are more prone to bradycardia.
- Heart rate may also fall below 60 BPM during sleep, which is normal.
- A low heart rate can also be common in athletes and other people who are physically fit. In these people, 55 would be a good resting heart rate.
What Are Normal Heart Rates by Age?
To find your heart rate, check your pulse, which can be felt on your:
- Wrists
- Inside of the elbow
- Side of the neck
- Top of the foot
Place your finger (not your thumb) over your pulse and count the number of beats in 60 seconds to get your heart rate.
Normal heart rates by age are as follows in the table below:
| 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 |
What Are Symptoms of a Slow Heart Rate?
A slow heart rate (bradycardia) may cause insufficient blood flow to the brain which can result in symptoms such as:
- Fatigue
- Weakness
- Dizziness
- Lightheadedness
- Fainting (or near-fainting) spells
- Confusion
- Shortness of breath
- Difficulty exercising
- Cardiac arrest (in severe cases)
What Causes a Slow Heart Rate?
Causes of a slow heart rate (bradycardia) may include:
- Problems with the sinoatrial (SA) node, considered the heart’s natural pacemaker
- Problems in the conduction pathways of the heart that don’t allow electrical impulses to pass properly from the atria to the ventricles
- Metabolic problems such as low thyroid hormone (hypothyroidism)
- Heart damage from heart disease or a heart attack
- Some heart medications that have slow heart rate as a side effect
What Is the Treatment for a Slow Heart Rate?
If a slow heart rate (bradycardia) only happens occasionally or is borderline, treatment may not be needed.
For people who are athletes or who are physically fit who have a slow heart rate, no treatment is needed.
Treatment for severe or prolonged heart rate may include:
- Adjusting or discontinuing medications that cause slow heart rate as a side effect
- Never stop taking a medication or change the dosage or regimen without first talking to your doctor
- Pacemaker to regulate the heart’s rhythm
From 
https://www.heart.org/
https://emedicine.medscape.com/article/2172054-overview#a2
https://www.cdc.gov/physicalactivity/basics/measuring/heartrate.htm
https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/bradycardia--slow-heart-rate
https://www.upmc.com/services/south-central-pa/heart-vascular/heart/heart-rhythm-disorders/bradycardia