That pounding sensation in your chest is your heart contracting with more force or speed than usual, and you’re becoming aware of it. This is called a palpitation, and it’s one of the most common reasons people visit a primary care doctor. Most of the time, palpitations are harmless and temporary. But sometimes they signal something worth investigating.
What’s Actually Happening in Your Chest
Your heart rate and the force of each beat are controlled by your autonomic nervous system, the part of your nervous system that runs on autopilot. When the sympathetic branch activates (the “fight or flight” side), it tells your heart to pump harder and faster. That’s the pounding you feel. It can happen because of a genuine threat, a stressful email, your third cup of coffee, or sometimes for no obvious reason at all.
Normally, you don’t notice your heartbeat. You start feeling it when the beats are stronger, faster, or irregular enough to register in your conscious awareness. The sensation might feel like thumping, fluttering, racing, or skipping. All of these fall under the umbrella of palpitations, and they can originate from very different causes.
Stress and Anxiety Are the Most Common Triggers
Anxiety causes a surge of adrenaline that directly increases your heart rate and contraction force. The heart stays in a regular rhythm, just a faster and stronger one. This is the most frequent explanation for palpitations, especially in younger adults without other health conditions.
Panic attacks deserve special mention because they can mimic a cardiac event convincingly. During a panic attack, your heart may race to 120 or 130 beats per minute, and you may also feel chest tightness, nausea, a choking sensation, or a sense of losing control. These episodes typically peak within minutes and resolve within about 30 minutes. The key distinction: in anxiety, your heart rhythm stays regular even though it’s fast. If you place two fingers on your wrist and feel a steady, even pulse, that’s reassuring.
Caffeine, Dehydration, and Other Everyday Causes
Before assuming something is wrong, consider the basics. Caffeine directly stimulates your heart and is one of the most common palpitation triggers. Alcohol does the same, particularly in larger amounts. Dehydration reduces your blood volume, forcing your heart to work harder to circulate the same amount of oxygen. Poor sleep, skipped meals, and intense exercise can all produce noticeable pounding.
Certain medications and supplements can also cause palpitations. Decongestants, asthma inhalers, stimulant medications for ADHD, and some herbal supplements (especially those containing ephedra or high-dose caffeine) are known culprits. If the pounding started around the same time you began a new medication, that connection is worth exploring.
When an Irregular Rhythm Is the Cause
Sometimes palpitations reflect an actual electrical problem in the heart. The two most common types are atrial fibrillation (AFib) and supraventricular tachycardia (SVT), and they feel quite different from each other.
AFib produces a chaotic, irregular rhythm. The upper chambers of the heart fire erratic electrical signals more than 300 times per minute, causing them to quiver instead of contracting normally. What you feel is an unpredictable, jumbled heartbeat. If you check your pulse during an episode, it will feel uneven, with no consistent spacing between beats. AFib episodes can last hours or even days, which is one way to distinguish them from panic attacks.
SVT, by contrast, produces a very fast but regular rhythm, sometimes reaching 200 beats per minute. It often starts and stops abruptly, like a switch being flipped. You might feel a sudden racing in your chest that lasts minutes to hours, then stops just as suddenly. SVT is usually not dangerous, but the episodes can be frightening and disruptive.
The simplest thing you can do during an episode is check your pulse. Press two fingers against the inside of your wrist and pay attention to whether the beats are evenly spaced or erratic. A regular but fast pulse points toward anxiety or SVT. An irregular, unpredictable pulse suggests AFib and warrants medical evaluation.
Thyroid Problems and Electrolyte Imbalances
An overactive thyroid gland is a well-established cause of palpitations. The thyroid controls your metabolic rate, and when it produces too much hormone, your entire cardiovascular system speeds up. A fast resting heart rate is recorded in nearly all patients with hyperthyroidism, and cardiac output can increase 50% to 300% above normal. Other signs include unexplained weight loss, heat intolerance, trembling hands, and feeling wired or anxious without a clear reason.
Low levels of magnesium and potassium also make the heart more electrically excitable, which can produce extra beats or pounding sensations. Data from the Framingham Heart Study found that even modest drops in magnesium levels increased the risk of frequent premature heartbeats. These electrolyte imbalances are especially common if you’re taking diuretics (water pills), sweating heavily, eating poorly, or drinking a lot of alcohol. A basic blood panel can identify these deficiencies quickly.
How Palpitations Are Evaluated
If you see a doctor about palpitations, the initial workup is straightforward. You’ll get a standard 12-lead ECG, which records your heart’s electrical activity for about 10 seconds. This can catch rhythm abnormalities if they happen to be occurring during the test, but a normal result doesn’t rule out a cardiac cause since many rhythm problems come and go.
Baseline blood work typically includes a complete blood count, electrolyte levels, kidney function, and thyroid tests. This screens for anemia, low potassium or magnesium, and thyroid dysfunction in one round of testing.
If the ECG is normal but suspicion remains, the next step is usually an ambulatory heart monitor. A Holter monitor records continuously for 24 hours, which works well if your symptoms happen daily. For less frequent episodes, an event monitor can be worn for up to 30 days, capturing your rhythm whenever symptoms occur. If palpitations happen during physical activity, an exercise stress test may be ordered since exertional symptoms carry higher risk.
Smartwatches as a Screening Tool
Consumer smartwatches with ECG capability have become surprisingly accurate at detecting AFib. A 2025 meta-analysis found that smartwatch ECGs detect atrial fibrillation with 95% sensitivity and 97% specificity overall. Apple Watch achieved 94% sensitivity, Samsung devices 97%, and the Withings ScanWatch 89%. These aren’t replacements for medical-grade monitoring, but recording an ECG on your wrist during an episode gives your doctor real data to work with, which is far more useful than trying to describe what you felt after the fact.
Patterns That Need Prompt Attention
Most palpitations are benign, but certain combinations of symptoms change the picture. Pounding accompanied by chest pain, fainting, severe dizziness, or significant shortness of breath warrants emergency evaluation. These can indicate a sustained arrhythmia or reduced blood flow to the heart.
Other patterns worth bringing to a doctor sooner rather than later: episodes that last longer than a few minutes and happen repeatedly, palpitations that occur during exercise rather than at rest, a pulse that feels chaotic or irregular, or pounding that comes with lightheadedness or near-fainting. A family history of sudden cardiac death or heart rhythm disorders also lowers the threshold for investigation.
For isolated episodes that happen at rest, resolve on their own, and aren’t accompanied by other symptoms, the most productive thing you can do is track the pattern. Note what you were doing, what you consumed, how long it lasted, and whether your pulse felt regular or irregular. That information helps a clinician decide what to test for and speeds up diagnosis considerably.