It can be unsettling when your heart starts racing. Maybe you just sprinted to catch a bus, or maybe it came out of nowhere while sitting at your desk. Either way, it's hard not to wonder: Is this normal?

"Heart palpitations can be caused by a fast heart rate or extra or skipped heart beats that happen as the heart beats normally throughout the day," says Dr. Sadeer Al-Kindi, a cardiologist at Houston Methodist. "But sometimes they occur due to a more serious issue that may warrant attention."

Everyone has experienced heart palpitations at some point. So what causes these palpitations, and when should you be concerned about them?

What do heart palpitations feel like?

It's your heart's job to pump blood throughout your entire body, helping to deliver the oxygen and nutrients that keep you alive and healthy. This process is controlled by your heart's electrical system. With each beat, your heart squeezes in a coordinated fashion — and this steady rhythm keeps blood pumping through your body efficiently.

Heart palpitations are sensations of the heart beating outside of its usual rhythm.

"As technology evolves and we've put heart rate monitors on people more frequently, we're starting to realize that almost everyone experiences extra and skipped beats," explains Dr. Al-Kindi.

This goes unnoticed in most cases. When heart palpitations are felt, the sensations can vary widely. It might feel like your heart is fluttering, or you may describe it as racing or pounding in your chest. Palpitations can also be felt in the throat and neck. These episodes typically don't last long, just a few seconds or minutes.

Are heart palpitations dangerous?

How often your heart beats can be affected by many things, with the most classic example being your activity level. "The harder your body is working, the more blood your heart needs to pump," explains Dr. Al-Kindi. "So the rate at which your heart beats must increase to achieve this."

Things that increase your heart rate can make experiencing skipped or extra beats more likely, but a faulty electrical system can, too — the latter of which can sometimes be life-threatening.

"Most heart palpitations aren't cause for concern," says Dr. Al-Kindi. "But it's important to consider the underlying cause and understand whether this is part of the heart's normal function or the result of a serious issue that requires treatment."

The causes of heart palpitations include:

• Stress, panic, fear and anxiety: Emotional stress can trigger the release of adrenaline, which increases heart rate
• Caffeine and alcohol: These stimulants can make the heart beat faster and harder
• Exercise: Intense physical activity can cause temporary palpitations
• Recreational drug use: Amphetamines and cocaine can lead to an increased heart rate
• Thyroid issues: An overactive thyroid can lead to an elevated heart rate
• Certain medications: Asthma inhalers, beta blockers and thyroid medications can increase heart rate
• Underlying heart issue: An irregular heartbeat, called arrhythmia, can cause the heart to beat too slow or too fast

Some of these causes are more serious than others. For instance, although occasionally harmless, some types of arrhythmias can have life-threatening consequences.

"Atrial fibrillation (AFib), a type of irregular heartbeat, can interfere with your heart's ability to pump enough blood to the rest of your body," warns Dr. Al-Kindi. "Left untreated, AFib can lead to heart failure and stroke."

The lifestyle factors that trigger heart palpitations are much less concerning, often just making the occurrence of extra or skipped beats more frequent. That said, people with existing arrhythmias may need to avoid these triggers, as they can make an irregular heartbeat more severe.

When to see a doctor about heart palpitations

With such a wide range of causes, how do you know when you should be worried about heart palpitations?

Consult your doctor if:

• They're accompanied by chest pain, dizziness, shortness of breath or fainting
• They persist for an extended period of time (more than a few minutes)
• They're worsening or occurring more frequently over time
• You are at high risk of developing heart disease
• You have an existing heart issue, including heart disease

Whether it's reassurance, monitoring or medical intervention, addressing palpitations appropriately can provide peace of mind and improve overall heart health.

"We often start by checking thyroid function and performing tests that help rule out the more significant causes of palpitations, such as a dangerous arrhythmia," says Dr. Al-Kindi. "It's important to identify the cause so we can determine whether they need treatment or can be monitored or improved with lifestyle changes."