Heart palpitations are usually caused by premature heartbeats, stimulants, stress, or hormonal changes. They account for roughly 16% of complaints in general practice, making them one of the most common reasons people visit a doctor. The good news: in studies tracking patients who present with palpitations, about 31% of cases trace back to anxiety or panic, and many cardiac causes turn out to be harmless extra beats rather than dangerous rhythms.
How a Normal Heartbeat Goes Off-Script
Your heart has a built-in pacemaker, a cluster of specialized cells that fires electrical signals in a steady rhythm. Palpitations happen when something disrupts that rhythm, even briefly. The most common culprit is a premature beat, where a spot outside the normal pacemaker fires early and triggers a contraction before the heart has fully refilled with blood. The next beat then feels unusually strong because the heart has had extra time to fill. That “thump” or “flip-flop” sensation is what most people describe as a palpitation.
These premature beats can originate in the upper chambers (atria) or the lower chambers (ventricles). Either way, the mechanism is similar: a rogue patch of heart tissue depolarizes on its own or gets triggered by the preceding beat. In some people, mechanical strain on the heart muscle, like the tug of a floppy valve, can also spark extra electrical signals. This is why structural issues like mitral valve prolapse sometimes cause palpitations even in otherwise healthy hearts.
Caffeine, Alcohol, and Other Stimulants
Caffeine is the substance people suspect first, and for good reason. In excess, it stimulates the nervous system, raises levels of stress hormones in the blood, and increases heart rate. The threshold matters, though. Health guidelines suggest most adults can safely consume up to about 400 mg per day (roughly four standard cups of brewed coffee). A single cup can contain anywhere from 70 to 280 mg depending on how it’s brewed, and energy drinks range from 80 to 300 mg per serving. So it’s easy to overshoot without realizing it.
Interestingly, moderate habitual coffee drinking doesn’t appear to increase the risk of atrial fibrillation, the most common sustained irregular rhythm. Some research even shows the risk of atrial fibrillation drops by about 6% for every additional 300 mg of daily caffeine in regular drinkers. The palpitations people feel after coffee are more often isolated premature beats, not dangerous rhythms. That said, very high doses of caffeine have been shown experimentally to trigger serious ventricular arrhythmias, so moderation still counts.
Alcohol works differently. It directly irritates heart muscle cells and disrupts electrolyte balance, both of which make the heart more electrically unstable. Nicotine increases adrenaline release and heart rate. Recreational stimulants like cocaine and amphetamines are potent triggers for both palpitations and genuinely dangerous rhythms.
Stress, Anxiety, and the Adrenaline Connection
Anxiety and panic disorders account for nearly a third of palpitation cases in clinical studies. The link is straightforward: emotional stress activates the fight-or-flight response, flooding the bloodstream with adrenaline. Adrenaline speeds up the heart and makes it more likely to produce premature beats. The tricky part is that palpitations themselves cause anxiety, which produces more adrenaline, which causes more palpitations. Breaking that cycle often matters as much as treating the heart itself.
Sleep deprivation and chronic stress work through the same pathway. They keep baseline adrenaline levels elevated, which lowers the threshold for extra beats. Many people notice palpitations most when they’re lying in bed at night, partly because there’s less noise and distraction to mask the sensation, and partly because the body is still winding down from the day’s stress hormones.
Thyroid Problems and Hormonal Shifts
An overactive thyroid gland is one of the most important medical causes to rule out. Thyroid hormones directly increase heart rate and cardiac output, and even mildly elevated levels significantly raise the risk of irregular rhythms. In one study, people over 60 with low TSH levels (a marker of excess thyroid hormone) had a 28% incidence of atrial fibrillation, compared to 11% in those with normal levels. Overall, suppressed TSH was associated with a more than fivefold higher incidence of atrial fibrillation.
What’s notable is that subclinical hyperthyroidism, where thyroid hormone levels still look normal on a blood test but TSH is suppressed, carries almost the same arrhythmia risk as full-blown hyperthyroidism. This is why doctors often check thyroid function when evaluating palpitations, even if you don’t have other thyroid symptoms like weight loss or tremor.
Hormonal changes during pregnancy, menstruation, and menopause can also trigger palpitations. Blood volume increases significantly during pregnancy, forcing the heart to work harder. Fluctuating estrogen levels around menopause affect the autonomic nervous system in ways that make palpitations more frequent.
Low Potassium and Magnesium
Potassium is the mineral most directly responsible for keeping heart cells electrically stable. Normal blood potassium runs between 3.5 and 5.3 mmol/L. When levels dip into the moderate range of 2.5 to 3.0 mmol/L, the electrical gradient across heart cell membranes becomes exaggerated, making cells more prone to firing at the wrong time. Severe drops below 2.5 mmol/L are life-threatening and can cause cardiac arrest.
You don’t need a dramatic deficiency to notice effects. Mild drops from heavy sweating, diarrhea, vomiting, or diuretic medications can produce noticeable skipped beats. Magnesium works alongside potassium to stabilize heart cell membranes, and low magnesium makes it harder for the body to correct low potassium. Both minerals are depleted by alcohol, excessive caffeine, and many common medications.
Medications That Trigger Palpitations
Several common drug classes can cause palpitations as a side effect. Asthma inhalers that contain beta-agonists (the “rescue” inhalers that open airways quickly) stimulate the same receptors in the heart that adrenaline does. Theophylline, an older oral medication for breathing problems, is associated with atrial fibrillation, especially when first started. Oral corticosteroids, commonly prescribed for asthma flares or inflammatory conditions, also raise the risk.
Over-the-counter decongestants containing pseudoephedrine or phenylephrine narrow blood vessels to relieve congestion, but they also raise heart rate and blood pressure. Thyroid replacement medication can cause palpitations if the dose is too high. Some antidepressants, ADHD stimulants, and diet pills that affect adrenaline or serotonin pathways are frequent offenders as well. If palpitations started around the same time as a new medication, that connection is worth investigating.
Structural Heart Conditions
Mitral valve prolapse is the most common structural cause of palpitations in otherwise healthy people. It occurs when the flaps of the mitral valve (which separates the left atrium from the left ventricle) become floppy and don’t close tightly. Most people with this condition never develop symptoms, but when they do, palpitations are the hallmark complaint. The physical strain of the prolapsing valve on the nearby heart muscle can generate extra electrical signals, particularly from the papillary muscles that anchor the valve.
Other structural issues, including thickened heart muscle (cardiomyopathy), scarring from a prior heart attack, or congenital abnormalities in the heart’s electrical wiring, can also produce palpitations. These causes are less common but more clinically significant because they carry a higher risk of dangerous rhythms.
Red Flags Worth Knowing
Most palpitations are harmless, but certain accompanying symptoms suggest something more serious. A resting heart rate above 120 or below 45 beats per minute, fainting or near-fainting (especially if you injure yourself falling), chest pain, and significant shortness of breath all warrant prompt medical evaluation. A family history of sudden cardiac death is another important risk factor that changes how aggressively palpitations should be investigated.
Palpitations that occur only with exertion, last for extended periods, or start and stop abruptly (rather than gradually speeding up and slowing down) are more likely to represent a true arrhythmia rather than simple premature beats. Isolated skipped beats that come and go, feel worse with caffeine or poor sleep, and happen in someone with no other heart disease are almost always benign.