The main cause of heart palpitations is premature heartbeats, specifically premature ventricular contractions (PVCs) and premature atrial contractions (PACs). These are extra beats that fire slightly out of rhythm, creating the sensation of a skipped, fluttering, or pounding heart. They are remarkably common: when healthy young adults with no heart disease wore heart monitors for 24 hours, over 50% had PVCs. On a standard ECG, which captures only a brief snapshot, PVCs show up in 1% to 4% of the general population. In the vast majority of cases, they are harmless.
Why You Feel Your Heart at All
Your heart normally beats without you noticing it. You have sensory nerve fibers embedded throughout the heart that send beat-to-beat information up to the brain through two main routes: the vagus nerve and spinal cord pathways. This signal travels through relay stations in the brainstem and eventually reaches areas of the brain involved in body awareness and emotion. The process of sensing your own heartbeat is called cardioception.
Most of the time, your brain filters out this steady stream of cardiac data. Palpitations happen when something disrupts the expected rhythm or force of a heartbeat, and the brain flags it as unusual. A premature beat, a sudden surge in heart rate, or an abnormally strong contraction can all cross that threshold. This is why palpitations feel so distinct: your nervous system is essentially alerting you that something changed, even if the change is benign.
Common Triggers for Premature Beats
Premature beats can happen on their own with no identifiable trigger, but several everyday factors make them more frequent. Caffeine, alcohol, and nicotine all stimulate the heart or alter its electrical signaling. Dehydration and poor sleep are underappreciated triggers. Stress and anxiety ramp up adrenaline, which increases both heart rate and the likelihood of extra beats. Many people notice palpitations more when lying down at night simply because the quiet environment makes the heartbeat more perceptible.
Exercise can provoke palpitations in some people and suppress them in others. During intense physical activity, the heart’s electrical system is under higher demand, which occasionally produces stray beats. For most healthy people, exercise-related palpitations are not dangerous, but palpitations that consistently occur during exertion rather than at rest deserve a closer look.
Medical Conditions That Cause Palpitations
Thyroid Problems
An overactive thyroid gland is one of the most important medical causes. Excess thyroid hormone increases the sensitivity of the heart’s receptors to adrenaline, producing a faster resting heart rate and a shortened recovery time between beats. The result mimics the feeling of a constant adrenaline rush: racing heart, pounding in the chest, and a sense of restlessness. Beta-blocker medications can slow the heart rate, but the underlying thyroid condition needs treatment for the palpitations to fully resolve.
Anemia
When your blood carries less oxygen than normal, your heart compensates by beating faster and harder to keep oxygen delivery adequate. This compensatory response often produces noticeable palpitations. Iron deficiency is the most common culprit. The heart can generally tolerate mild anemia, but as hemoglobin drops toward about 7 g/dL, the heart begins transitioning from a compensated high-output state to genuine strain. Palpitations from anemia typically improve once iron levels are restored.
Low Magnesium and Potassium
Both minerals are essential for stable electrical signaling in the heart. When magnesium drops below normal levels, it disrupts the ion channels that regulate each heartbeat, making cardiac cells electrically unstable. This instability can produce extra beats or more serious rhythm disturbances. Magnesium deficiency is common and easy to miss because standard blood tests don’t always reflect what’s stored in your tissues. Low potassium has a similar effect, and the two deficiencies often occur together, especially in people who take certain blood pressure medications or experience frequent dehydration.
Cardiac Arrhythmias
While most palpitations come from isolated premature beats, some are caused by sustained abnormal heart rhythms. Atrial fibrillation is the most common of these. It produces a chaotic, irregularly irregular heartbeat, often with a rate between 80 and 180 beats per minute. People typically describe it as a quivering or fluttering sensation that lasts minutes to hours rather than a single skipped beat. Other arrhythmias that cause palpitations include atrial flutter, which feels more regular and rapid, and supraventricular tachycardia, which often starts and stops abruptly.
Medications That Trigger Palpitations
Several classes of drugs can provoke palpitations as a side effect. Asthma inhalers containing bronchodilators like salbutamol or formoterol stimulate receptors in the heart as well as the lungs. In clinical trials, about 13% of patients using formoterol experienced a fast heart rhythm. Decongestants containing pseudoephedrine have a similar stimulant effect. Certain medications that block the nervous system’s “rest and digest” signals (used for overactive bladder, some stomach conditions, and anesthesia) can also shift the heart toward a faster, more palpitation-prone state.
If palpitations started or worsened after beginning a new medication, that connection is worth raising with whoever prescribed it. Stopping or switching the medication often resolves the issue.
How Palpitations Are Diagnosed
The challenge with diagnosing palpitations is that they tend to come and go unpredictably. A standard ECG records only about 10 seconds of heart activity, so it catches the cause only if symptoms happen to occur during the test. A 24-hour Holter monitor improves the window, but research shows it provides a clinical diagnosis in only about 1.8% of cases, largely because most people’s palpitations don’t conveniently occur within that single day.
Patient-activated event recorders, worn for up to two weeks, are far more effective. In a study comparing the two approaches, the event recorder identified the underlying arrhythmia in 89% of patients, with an average time to diagnosis of about 9 days. Notably, no diagnoses were made during the first 24 hours of event recording, which highlights exactly why the shorter Holter monitor misses so much. For infrequent palpitations, longer monitoring almost always yields better answers.
Blood tests for thyroid function, hemoglobin, potassium, and magnesium are part of a standard workup because these are all correctable causes that don’t require cardiac treatment.
When Palpitations Signal Something Serious
Most palpitations are harmless, but certain accompanying symptoms change the picture. Palpitations paired with chest pain, fainting, severe dizziness, or significant shortness of breath warrant emergency evaluation. A personal or family history of heart disease, sudden cardiac death, or known arrhythmias also raises the stakes. Palpitations that last many minutes, come with a very rapid heart rate you can feel in your neck, or leave you lightheaded enough that you need to sit down are qualitatively different from the occasional skipped beat at rest.
The distinction matters because sustained arrhythmias like atrial fibrillation carry real risks, including stroke, while isolated premature beats in an otherwise healthy heart generally do not. Getting a recording of your heart rhythm during symptoms is the single most useful step in sorting out which category your palpitations fall into.