Your heart rate changes throughout the day — ranging from low when you’re lying down to high when you exercise. During regular activities, it’s normal for your heart rate to be between 60 and 100 beats per minute (bpm), whereas anything higher than 100 bpm when you’re at rest is called tachycardia. Although tachycardia is sometimes due to a heart problem, it can also have other causes. To ensure you stay in good health, it’s important to be aware of the possible causes of a rapid heart rate.

1. Strenuous Exercise

According to Allina Health, vigorous exercise can cause your heart rate to reach as high as 160 bpm — although if you’re 60 years old or above, it should never go beyond 128 bpm. After you finish exercising, your heart rate should return to its normal rest rate within about 10 minutes.

2. Low Fitness Levels

You may experience a significant increase in heart rate during even mild exertion if your fitness levels are low. Increasing the amount of cardiovascular exercise you do on a weekly basis may gradually help to regulate your heart rate.

3. Stress

When you’re in a stressful situation, your body responds by releasing adrenaline to prepare you for the fight or flight response. This has multiple effects on your body, including an increase in heart rate. An occasional stressful event has no negative impacts on your health, but chronic stress can lead to various problems — including heart disease, according to GoodRx Health.

4. Fever

Fever is a sign you’re fighting an infection, which means your body is under physical stress. It is normal for a fever to be accompanied by an increase in heart rate.

5. Arrhythmia

Arrhythmia is a collection of conditions that cause an irregular heartbeat due to incorrect electrical signaling. It can lead to a heart rate that is either too fast or too slow.

6. Atrial Fibrillation

One common form of arrhythmia is atrial fibrillation. In this condition, the heartbeat is irregular and rapid. It occurs because a signaling problem in the upper chambers (called the atria) causes the chambers to beat too quickly. The condition can also be fatal, as it increases the risk of a stroke. This can happen if the blood that collects in the atria forms a clot and then travels to the brain after it leaves the heart.

7. Hypoglycemia

Your blood sugar levels need to remain high enough to provide your organs and muscles with energy. Hypoglycemia occurs if your blood sugar drops below optimal levels. There are several reasons why you may experience low blood sugar, according to the Mayo Clinic, and it is most often a side effect of medications used to treat diabetes. Hypoglycemia can also be due to high alcohol consumption over a long period of time (which can result in your liver failing to release glucose when your blood sugar drops) and certain other medical conditions.

8. Sugary Foods and Beverages

On the flip side, a fast heart rate can be due to hyperglycemia: high blood sugar levels. This tends to happen if you consume too much sugar in your diet.

9. Anemia

Anemia is a condition where you have insufficient red blood cells to transport oxygen. To deliver oxygen to your organs as fast as they need it, your heart may compensate by beating more rapidly. The most common cause of anemia is an iron deficiency. This can be due to insufficient iron in your diet, a problem with iron absorption, heavy menstrual cycles, or gastrointestinal issues like stomach ulcers.

10. Hypotension

Hypotension is defined as a fall in blood pressure to 90/60 mmHg or lower. To compensate, your blood vessels need to constrict or your heart rate needs to increase. Hypotension can be the result of a medical condition or the side effect of a medication or supplement. Alternatively, you may notice a brief drop in blood pressure when you stand up (called postural hypotension), after eating (particularly if you have nervous system disease), or when you’re dehydrated. Usually, lifestyle changes or adjusting your medication dosage (according to the advice of your doctor) is sufficient to treat the condition.

11. Overactive Thyroid

Hyperthyroidism is a condition where your thyroid is overactive and creates too much thyroid hormone. As well as an increased heart rate, Mayo Clinic says symptoms of this condition include weight loss, nervousness, increased appetite, problems sleeping, tremors and increased sensitivity to heat, among several others.

12. Overuse of Stimulants

Stimulants include caffeine, over-the-counter decongestants, alcohol and tobacco, as well as illicit drugs like cocaine and amphetamines. All these can lead to an increase in heart rate after consumption. In addition, smoking can lead to a higher heart rate during rest even when the nicotine levels in your blood have dropped. This is because damage to your lungs means your heart needs to work harder. Using illegal drugs can have a similar effect — they can damage your heart over time, resulting in congestive heart failure and a consistent increase in heart rate.

13. Low-Quality Sleep

You may find your heart rate remains high throughout the day if your sleep was low quality the night before. Poor-quality sleep is often due to insufficient hours in bed or the use of stimulants late in the day.

14. Medication and Supplements

Many medications can cause your heart rate to rise. This includes prescription drugs for conditions like asthma, high blood pressure, depression and anxiety, as well as over-the-counter medications for colds, flu and allergies.

There is even more potential for supplements to cause side effects like a rapid heart rate because they are unregulated by the Food and Drug Administration (FDA). This means you may be unaware of exactly what you are ingesting. Supplements to boost energy levels, balance hormones and help with weight loss are among the most likely to raise your heart rate.

15. A Previous Heart Attack

If you suffered a heart attack in the past, you will always have the worry that could have another in the future. This can make a fast heart rate particularly concerning. Since your heart may be damaged, some changes to its rhythm are a possibility — but this doesn’t necessarily mean you are at immediate risk. By making the lifestyle changes your physician recommends, you can protect yourself from future heart problems.

Signs and Symptoms of Concern

Unless you wear a device that tracks your heart rate, it can be difficult to keep track of how fast your heart is beating. In addition to checking your pulse whenever you feel your heart may be racing, it’s helpful to be aware of the common signs and symptoms of tachycardia. These include:

  • Lightheadedness or dizziness
  • Fatigue or weakness
  • Shortness of breath or difficulty breathing
  • Fainting
  • Pain or tightness in your chest
  • Nausea
  • Difficulty walking

Next Steps

If you are concerned your heart rate may be too rapid, it’s worth reading more about tachycardia from a reputable source like Mayo Clinic. In this article, you’ll find information about the different types of tachycardia, learn about treatment for atrial fibrillation and find out when your symptoms mean you should seek medical attention.

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