Heart palpitations happen when you become aware of your own heartbeat in a way that feels abnormal. The sensation might feel like a flutter, a racing pulse, a thud, or a skipped beat. Roughly 6 to 11% of people experience palpitations in any given year, and about 16% of primary care patients have reported them. Most of the time, the cause is harmless, but understanding why they happen helps you sort the ordinary from the concerning.
What’s Actually Happening in Your Chest
The most common source of that “skipped beat” feeling is an ectopic heartbeat, which simply means your heart contracts slightly too soon. This premature beat can originate in the upper chambers of the heart (called a premature atrial contraction) or the lower chambers (a premature ventricular contraction). Neither is typically dangerous. What you’re feeling isn’t actually a skipped beat. It’s the pause that follows the early contraction, then the stronger-than-usual beat that comes next as the heart resets its rhythm. That forceful thump is what registers in your awareness.
Beyond ectopic beats, palpitations can also reflect a genuinely faster heart rate. Your resting heart normally beats 60 to 100 times per minute without you noticing. When something pushes that rate higher or makes the rhythm irregular, the sensation breaks through into conscious awareness.
Stress, Adrenaline, and the Fight-or-Flight Response
Your sympathetic nervous system is designed to speed up your heart when you’re stressed, frightened, or physically exerting yourself. It does this by releasing adrenaline and norepinephrine, chemical signals that tell the heart to pump faster and harder so your muscles get more oxygen. This is the classic fight-or-flight response, and it’s completely normal during exercise, a sudden scare, or a tense moment.
The problem is that chronic stress, anxiety, and panic attacks activate this same system when there’s no physical threat. Your heart races or pounds even though you’re sitting at your desk or lying in bed. Over time, you can become hyperaware of your heartbeat, which makes each normal variation feel alarming. This creates a feedback loop: the palpitation triggers anxiety, the anxiety releases more adrenaline, and the cycle continues.
Caffeine, Alcohol, and Other Triggers
Several everyday substances can nudge your heart rhythm off its usual pattern. Caffeine is the most commonly blamed trigger, though sensitivity varies widely between people. Some can drink multiple cups of coffee with no effect, while others notice palpitations after a single espresso. Alcohol is another well-established trigger. Even moderate drinking can provoke episodes of irregular rhythm in the upper chambers of the heart, sometimes called “holiday heart” because it often shows up after heavy social drinking.
Nicotine, whether from cigarettes or vaping, stimulates adrenaline release and can increase heart rate. Dehydration and skipping meals can also set off palpitations, because low blood volume and low blood sugar both force the heart to compensate by beating faster or harder.
Medications That Can Cause Palpitations
Certain medications list palpitations as a known side effect. Asthma inhalers that contain bronchodilators like albuterol work by relaxing airway muscles, but they also stimulate the heart. Studies have found that nebulized albuterol can trigger a fast heart rhythm in up to 21% of cases. Theophylline, another asthma medication, carries a similar risk.
Over-the-counter decongestants containing pseudoephedrine or phenylephrine narrow blood vessels to reduce nasal congestion, but that same blood-vessel-tightening effect can raise heart rate and blood pressure. Stimulant medications used for ADHD, diet pills, and even some herbal supplements (particularly those containing ephedra or high-dose guarana) can all produce the same effect. If palpitations started around the same time you began a new medication, that connection is worth investigating.
Thyroid Problems and Hormonal Shifts
An overactive thyroid gland produces excess thyroid hormone, which directly affects heart muscle cells. Thyroid hormone regulates several components of the signaling system that controls heart rate, including the receptors that respond to adrenaline and the enzymes that amplify that signal. The result is a heart that beats faster and sometimes irregularly, even when you’re calm. Palpitations are one of the earliest and most noticeable symptoms of hyperthyroidism, often appearing alongside weight loss, heat intolerance, and trembling hands.
Hormonal fluctuations during menstruation, pregnancy, and menopause can also trigger palpitations. Estrogen and progesterone influence heart rate and blood volume, and shifts in these hormones can temporarily alter how the heart beats. Palpitations during pregnancy are particularly common because blood volume increases by nearly 50%, forcing the heart to work harder.
Anemia and Low Iron
When you don’t have enough healthy red blood cells to carry oxygen, your heart compensates by pumping faster and harder. This is why palpitations are a hallmark symptom of iron deficiency anemia. The mechanism is straightforward: low hemoglobin reduces the blood’s oxygen-carrying capacity, which triggers a drop in blood pressure. Your body responds with a surge of sympathetic nervous system activity, the same fight-or-flight chemicals that speed up the heart under stress. In severe anemia, this compensatory response can be so pronounced that it mimics heart failure, though it reverses completely once the anemia is corrected.
If your palpitations come with fatigue, pale skin, dizziness, or shortness of breath on exertion, low iron is a common and very treatable explanation.
Heart Conditions That Cause Palpitations
Most palpitations aren’t caused by heart disease, but some are. Atrial fibrillation, where the upper chambers of the heart quiver chaotically instead of contracting in rhythm, is the most common sustained arrhythmia and often presents as palpitations with an irregular pulse. It’s more common after age 60 but can occur earlier, especially in people who drink heavily or have thyroid disease.
Other structural or electrical problems, like abnormal conduction pathways (such as Wolff-Parkinson-White syndrome), valve disorders, or cardiomyopathy, can also produce palpitations. These are less common but more serious, and they tend to come with additional symptoms like fainting, chest pain, or significant shortness of breath.
How Palpitations Are Diagnosed
The challenge with palpitations is that they often come and go. A standard electrocardiogram (ECG) records your heart rhythm for about 10 seconds, which is useful if the palpitation is happening right then but often catches a perfectly normal rhythm. That’s why doctors frequently turn to ambulatory ECG monitoring, where you wear a portable recording device for 24 hours to several weeks. The goal is to capture what your heart is doing at the exact moment you feel symptoms, creating a direct correlation between the sensation and the electrical activity.
For palpitations that happen rarely, longer-term monitors or event recorders that you activate when symptoms strike can be more useful. Blood tests to check thyroid function, hemoglobin levels, and electrolytes are also standard, since these reveal many of the non-cardiac causes.
Symptoms That Need Immediate Attention
Isolated palpitations that last a few seconds and resolve on their own are rarely dangerous. The picture changes when palpitations come alongside chest pain, significant shortness of breath, or fainting. These combinations can signal a serious arrhythmia or another cardiac event that needs emergency evaluation. Palpitations that persist for minutes without stopping, especially with a heart rate above 150 beats per minute, also warrant urgent care. The same applies if you feel lightheaded to the point of nearly passing out, because that suggests your heart isn’t pumping enough blood to your brain during the episode.