A dangerous heart rate is a heart rate that is either too fast or too slow. This threshold is different for everyone and is dependent on your age, sex, weight, and how fit you are. 

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

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Dangerous Heart Rate

There is no clear line between a safe heart rate and a dangerous heart rate. 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.

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 find your maximum heart rate by subtracting your age from 220.

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 while you are at rest.

Similarly, your heart rate may be dangerous if it is too low while you are at rest.

When Your Heart Rate Is High

Having a heart rate that's considered too high is called tachycardia. However, this is not always considered dangerous. In general, tachycardia refers to a heart rate that is above 100 beats per minute.

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

In severe cases, tachycardia can be dangerous and cause serious conditions such as loss of consciousness or heart attack.

Signs of Heart Attack

A heart attack is a potentially life-threatening event that requires immediate medical attention. In addition to an excessively high or low heart rate, other symptoms of heart attack can include:

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

Seek medical attention if you experience a sudden or severe onset of any of these symptoms.

When Your 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.

Signs of Abnormal Heart Rates In Children

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

What Is a Normal Heart Rate?

A person's ideal heart rate depends on many factors. 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 perfect for you.

Certain medications also impact heart rate. For example, beta-blockers slow a person's heart down, while decongestants can increase heart rate.

Heart rate also varies throughout the day and night. During exercise, your heart pumps faster to get oxygen to your hardworking muscles. At night, your heart rate tends to decrease.

You can measure your heart rate by taking your pulse—counting the number of heartbeats for one minute at the side of your neck, or the thumb side of your wrist.

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 doctor. 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.

Summary

In general, the normal resting heart rate for adults is 60–100 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.

A Word From Verywell

Realizing that your heart rate falls outside of what's considered normal can be alarming. If you have any concerns about your heart rate, see your healthcare provider. Most likely it isn't anything serious—but if it is, early detection and treatment can potentially be lifesaving.

Frequently Asked Questions

  • 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.

  • What is considered a normal heart rate?

    Normal resting heart rate for most adults is 60–100 beats per minute. Normal resting heart rate is higher in infants and children.

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.

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