What Is Considered a Dangerous Heart Rate?

Your heart rate may be dangerous if it regularly exceeds your maximum during exercise, especially if you are new to exercising and are pushing yourself too hard. Your heart rate is also considered dangerous if it is too high or too low while you are at rest.

Pulse reading on smart watch

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Those thresholds are different for everyone and depend on age, sex, weight, and fitness level. For example, someone who is very fit may be able to safely achieve faster heart rates during exercise and lower resting heart rates than someone who does not regularly exercise.

This article discusses normal heart rates and how excessively high or low heart rates can have a negative impact on your health.

Dangerous vs. Normal Heart Rate

Whether or not your heart rate is dangerous depends on your personal targets.

A normal resting heart rate for adults ranges from 60 to 100 beats per minute. However, you can have a resting heart rate outside this range that is perfectly fine for you. If you are very physically active, for example, a resting heart rate of 40 beats per minute may be your norm.

A high heart rate during exercise is considered safe as long as you don't exceed your maximum heart rate.

Maximum heart rate varies from person to person, but in general, you can figure out your maximum heart rate by subtracting your age from 220.

When Heart Rate Is Too High

Having a heart rate that's considered too high is called tachycardia. In general, tachycardia refers to a heart rate that is above 100 beats per minute. This can be dangerous, but isn't always.

There are different types of tachycardia. A higher heart rate naturally occurs when you're exercising, for example. You can also experience tachycardia during scary or stressful events, if you consume a lot of caffeine, or if you are a heavy smoker.

Tachycardia can also occur when the electrical signals in your heart that cause it to beat are firing abnormally. Because your heart is beating faster than it should, it can't fill back up completely. As a result, less blood is delivered to the rest of your body.

In some cases, tachycardia does not cause any symptoms. In others, it can cause:

  • Dizziness
  • Fainting
  • Pounding heartbeat
  • Chest pain or pressure
  • Shortness of breath
  • Palpitations (fast-beating, fluttering, or pounding heartbeats)
  • Tiredness

Frequently exceeding a safe maximum heart rate can be dangerous. This is because an overworked heart is less efficient at pumping blood throughout the body. This can result in loss of consciousness or heart attack.

Seek immediate medical attention if you experience a sudden or severe onset of any of these heart attack symptoms:

  • Chest pain or pressure
  • Jaw, arm, neck, or back pain
  • Difficulty breathing
  • Weakness
  • Dizziness/fainting
  • Fatigue
  • Nausea/vomiting

When Heart Rate Is Low

A heart rate that is considered too low is called bradycardia. This typically refers to a heart rate lower than 60 beats per minute for adults.

A low heart rate is not always abnormal. In fact, it can even be a sign of physical fitness.

For example, if you are an endurance athlete, your heart probably works very efficiently. Your normal heart rate could be closer to 40 or 50 beats per minute—or even lower. This means that your heart doesn't have to pump as fast to deliver oxygen to the rest of your body.

Bradycardia can also be a symptom of underlying medical conditions, however. Low heart rate can occur when electrical impulses don't travel along correct paths in the heart or when the structures that generate these electrical impulses—called nodes—are damaged.

Low heart rate can also occur with heart disease, heart attack, and other medical conditions such as hypothyroidism (underactive thyroid).

Symptoms of bradycardia are similar to those caused by a high heart rate. These can include:

  • Dizziness
  • Fainting
  • Difficulty breathing
  • Confusion
  • Weakness
  • Tiredness
  • Limited ability to exercise

Bradycardia can also lead to heart failure and changes in blood pressure (both high and low).

Dangerous Heart Rates in Children

Normal heart rates are higher in infants and children than adults. These numbers decrease as a child gets older.

Normal Heart Rates in Children
Age Heart Rate While Awake (Beats Per Minute) Heart Rate While Sleeping (Beats Per Minute)
Newborn 100-205 90-160
1 month to 1 year 100-180 90-160
1 to 3 years 98-140 80-120
3 to 5 years 80-120 65-100
6 to 12 years 75-118 58-90
13 to 18 years 60-100 50-90

Heart rates outside the normal range in children can be caused by some of the same issues that affect adults—the abnormal firing of electrical signals in the heart or damage to the heart. It can also be a side effect of medication.

It can be more difficult to know when a child is experiencing abnormal heart rates, especially if they are too young to talk. Older children might know that they feel faint or weak or are experiencing heart palpitations. Additional symptoms in younger kids can include:

  • Pale skin
  • Tiredness
  • Irritability
  • Difficulty feeding
  • Shortness of breath

When to See a Healthcare Provider

If you suspect that you or your child has a heart rate that is too high or too low, see your healthcare provider. You'll likely have testing done to determine the cause of your symptoms.

An electrocardiogram (ECG or EKG) is commonly the first test performed to determine the cause of an abnormal heart rate. During this test, electrodes are attached to your chest (and sometimes arms or legs) to detect the electrical impulses as they pass through your heart.

Your doctor might also have you wear a portable heart monitor for a day (or longer) to record your heartbeat for longer periods of time.

Be sure to tell them about any medications you are taking, as certain drugs impact heart rate. For example, beta-blockers slow a person's heart down, while decongestants can increase heart rate.

Summary

In general, the normal resting heart rate for adults is 60 to 100 beats per minute. However, heart rate varies from person to person, and your ideal heart rate might be higher or lower than this range.

Many factors can contribute to a change in heart rate, including exercising, consuming caffeine, smoking, and more. In some cases, a heart rate that is too high or too low can be a sign of underlying issues with the electrical impulses in your heart, or other medical conditions.

Frequently Asked Questions

  • How can I measure my heart rate?

    To measure your heart rate, place your index and middle fingers at the side of your neck or the inside of your wrist and count the number of pulses for one minute.

  • What heart rate indicates a heart attack?

    There is no specific heart rate that indicates a heart attack is occurring. Heart rate can be higher or lower than normal during this event.

  • At what heart rate should I go to the doctor?

    If your heart rate is consistently out of the normal range for adults, or if you are experiencing symptoms such as dizziness or shortness of breath, see your healthcare provider.

  • Does heart rate change throughout the day?

    Yes. During the day, when you're active, your heart pumps faster to get oxygen to your muscles. At night, when the body is at rest, your heart rate tends to decrease.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Harvard Health Publishing. Is a low heart rate worrisome?

  2. American Heart Association. Target Heart Rates Chart.

  3. American Heart Association. Tachycardia: Fast heart rate.

  4. Centers for Disease Control and Prevention. Heart attack symptoms, risk, and recovery.

  5. American Heart Association. Bradycardia: Slow heart rate.

  6. UpToDate. Heart rates in normal children.

  7. American Academy of Pediatrics. Fast, slow and irregular heartbeats (arrythmia).

By Aubrey Bailey, PT, DPT, CHT
Aubrey Bailey is a physical therapist and professor of anatomy and physiology with over a decade of experience providing in-person and online education for medical personnel and the general public, specializing in the areas of orthopedic injury, neurologic diseases, developmental disorders, and healthy living.