Heart palpitations are one of the most common reasons people seek medical attention for cardiac concerns. While the sensation can be frightening, the majority of palpitations are benign. However, some are caused by underlying conditions that blood tests can identify — conditions like thyroid dysfunction, anemia, electrolyte imbalances, and blood sugar abnormalities.

Understanding what’s causing your palpitations is essential. Some causes are easily correctable; others require monitoring or treatment. Blood tests play a crucial role in identifying or ruling out many of the metabolic and hormonal causes of palpitations, often pointing toward a solution that can eliminate symptoms entirely.

This article explores what heart palpitations actually are, what causes them, and what blood tests can reveal about the underlying reasons your heart isn’t beating as smoothly as it should.

Understanding Heart Palpitations

Heart palpitations are the subjective awareness of your own heartbeat — a sensation that your heart is beating too fast, too hard, too irregularly, or simply in a way that you notice when you normally wouldn’t. Under normal circumstances, we’re blissfully unaware of our heartbeat. The heart beats over 100,000 times per day, and we don’t feel most of them. When we become aware of our heartbeat — when it intrudes into consciousness — that’s a palpitation.

Palpitations are extremely common. Studies suggest that up to 16% of people experience them at some point, making them one of the most frequent reasons for both primary care and cardiology consultations. While the sensation can be alarming — anything involving the heart naturally causes concern — the vast majority of palpitations are benign. However, some are caused by underlying conditions that blood tests can identify, and some require cardiac evaluation to rule out significant arrhythmias.

What palpitations feel like:

People describe palpitations in many different ways, and the description can provide clues about what’s happening:

• Racing heart (tachycardia sensation): The sensation that your heart is beating much faster than normal, even at rest or with minimal activity. You might feel your heart “running away” or “going a mile a minute.” This often corresponds to actual tachycardia but can also occur with heightened awareness of a normal heart rate.
• Fluttering: A light, rapid sensation in the chest, often described as “butterflies,” a “fish flopping,” or “quivering.” This description is common in atrial fibrillation (AFib) and atrial flutter, where the atria beat rapidly and irregularly.
• Pounding or throbbing: An unusually forceful heartbeat that you can feel not just in your chest but potentially in your neck, ears, or even your head. This often reflects increased stroke volume (the amount of blood pumped with each beat) rather than increased rate — the heart is beating harder, not necessarily faster.
• Skipped beats: The sensation that your heart missed a beat, paused, or stopped briefly, often followed by a stronger-than-normal beat that may feel like a thump or kick. This classic description usually corresponds to premature beats (PACs or PVCs) — an early beat is followed by a compensatory pause, and the next beat is more forceful because the heart has had extra time to fill.
• Flip-flopping or flopping: A feeling that the heart is turning over, doing somersaults, or flopping like a fish. This is another common description of premature beats.
• Irregular rhythm: An awareness that beats are coming at uneven intervals rather than in a steady rhythm. May feel chaotic or unpredictable. Classic for atrial fibrillation.
• Hard or forceful beating: Unusually strong beats that seem to shake the whole chest. Can feel like the heart is trying to beat out of the chest. Often relates to increased contractility (strength of contraction) rather than rate.
• Fluttering in the throat: Some people feel palpitations more in the throat or neck than in the chest, particularly when the carotid arteries pulsate forcefully.

The location where palpitations are felt can vary — chest, throat, neck, or even the upper abdomen. Some people notice them primarily when lying down, particularly on the left side (when the heart is closest to the chest wall and vibrations transmit more readily). Others notice them at night when ambient noise is low and there are fewer distractions.

What’s actually happening during palpitations:

When you experience palpitations, one or more of the following may be occurring physiologically:

• Increased heart rate (tachycardia): The heart genuinely beating faster than the normal resting rate of 60-100 beats per minute. This can be:
  • Sinus tachycardia: Normal rhythm originating from the normal pacemaker (sinoatrial node), just faster. Common with exercise, anxiety, fever, anemia, hyperthyroidism, and many other conditions.
  • Supraventricular tachycardia (SVT): Rapid rhythms originating above the ventricles, including AVNRT and AVRT. Often cause sudden-onset episodes of very rapid heart rate.
  • Atrial fibrillation or flutter: Rapid, irregular (AFib) or regular (flutter) rhythms from the atria.
  • Ventricular tachycardia: Rapid rhythm originating in the ventricles; potentially dangerous.
• Premature beats (ectopic beats): Extra beats originating from somewhere other than the normal pacemaker. These include:
  • Premature atrial contractions (PACs): Early beats from the atria
  • Premature ventricular contractions (PVCs): Early beats from the ventricles
  The “skipped beat” sensation is usually a premature beat followed by a compensatory pause. The pause allows extra filling time, so the next beat is more forceful (you feel the thump). PACs and PVCs are extremely common — most people have some every day — and usually harmless.
• Arrhythmias: Abnormal heart rhythms beyond simple premature beats. Atrial fibrillation is the most common sustained arrhythmia. Others include atrial flutter, SVT variants, and ventricular arrhythmias.
• Increased stroke volume: Each heartbeat pumps more blood than usual. This occurs in anemia (compensating for reduced oxygen-carrying capacity), hyperthyroidism (increased metabolic demand), fever, anxiety, and other states. The forceful ejection of blood makes beats feel more prominent.
• Increased awareness without abnormality: Sometimes the heart is beating completely normally — normal rate, normal rhythm, normal force — but anxiety, heightened body awareness, positional factors (lying on left side), or simply a quiet environment makes you notice beats you’d normally ignore. This is still a real symptom that can be distressing, even if the heart itself is fine.

Common triggers for palpitations:

Many palpitations are triggered by identifiable factors. Recognizing triggers can help with both prevention and diagnosis:

• Caffeine: Coffee, tea, energy drinks, cola, chocolate, and caffeine-containing medications. Caffeine stimulates the heart and nervous system. Sensitivity varies — some people notice palpitations with one cup of coffee, others tolerate much more.
• Alcohol: Especially in larger amounts. “Holiday heart syndrome” is the term for atrial fibrillation triggered by heavy alcohol consumption, commonly seen after weekends or holidays. Even moderate amounts can trigger palpitations in susceptible individuals.
• Nicotine: Smoking, vaping, and nicotine replacement products. Nicotine is a stimulant that affects heart rate and rhythm.
• Stimulant medications: Decongestants (pseudoephedrine, phenylephrine), ADHD medications (amphetamines, methylphenidate), asthma inhalers (beta-agonists like albuterol), some weight loss supplements, and thyroid hormone (if dose too high).
• Recreational drugs: Cocaine, amphetamines, MDMA/ecstasy, and others are potent cardiovascular stimulants that can cause dangerous arrhythmias.
• Stress and anxiety: Emotional stress activates the sympathetic nervous system, releasing adrenaline and increasing heart rate and contractility. Even anticipation of a stressful event can trigger palpitations.
• Intense exercise: Normal to have increased heart rate during exercise, but some arrhythmias are exercise-induced. Palpitations during or immediately after intense exercise warrant evaluation.
• Lack of sleep: Sleep deprivation increases susceptibility to palpitations and arrhythmias. The stress of poor sleep activates the sympathetic nervous system.
• Dehydration: Affects blood volume, blood pressure, and electrolyte balance, all of which influence heart rhythm.
• Fever and illness: Fever increases metabolic demand and heart rate. Infections also trigger inflammatory and stress responses affecting the heart.
• Hormonal changes: Menstruation (particularly premenstrual period), pregnancy (blood volume increases 30-50%), perimenopause, and menopause are all associated with palpitations. Hormonal fluctuations affect autonomic nervous system function.
• Large meals: Especially high-carbohydrate meals. Blood flow shifts to the digestive system, heart rate increases, and insulin release can affect electrolytes. Some people notice palpitations specifically after eating.
• Position: Lying on the left side places the heart closer to the chest wall. Bending over can increase abdominal pressure. Some people notice palpitations only in certain positions.

When palpitations suggest an underlying condition:

Occasional palpitations triggered by obvious factors — too much coffee before a big meeting, a stressful presentation, vigorous exercise on a hot day — are usually benign and don’t require extensive investigation. Palpitations warranting medical evaluation include:

• Frequent episodes occurring without obvious triggers
• Prolonged episodes lasting minutes rather than just a few seconds
• Associated symptoms — dizziness, lightheadedness, shortness of breath, chest pain or pressure, near-fainting or fainting
• Palpitations that occur at rest without any apparent trigger
• Episodes that wake you from sleep
• Progressive worsening — episodes becoming more frequent, longer, or more intense over time
• Known heart disease or significant heart disease risk factors (hypertension, diabetes, high cholesterol, smoking history, family history)
• Family history of sudden cardiac death, arrhythmias, or inherited heart conditions
• Palpitations accompanied by other symptoms suggesting thyroid disease (weight changes, heat or cold intolerance), anemia (fatigue, pallor), or other systemic conditions
• Very rapid heart rate (over 150 beats per minute by your count or pulse)
• Sudden onset and sudden offset of rapid heartbeat (characteristic of SVT)

Warning signs requiring immediate medical attention:

Seek emergency care if palpitations are accompanied by:

• Chest pain, pressure, tightness, or discomfort
• Severe shortness of breath or difficulty breathing
• Fainting (syncope) or near-fainting (presyncope)
• Severe dizziness or feeling like you might pass out
• Confusion or altered mental status
• Prolonged rapid heartbeat that doesn’t slow down with rest or vagal maneuvers
• Palpitations in someone with known heart disease or heart failure
• Extremely rapid heart rate (over 150-200 bpm)
• Blue or gray color of lips or fingertips

Thyroid Dysfunction: A Major Cause

Thyroid disorders are among the most common — and most important — causes of heart palpitations. The thyroid gland produces hormones that regulate metabolism throughout the body, and the heart is exquisitely sensitive to thyroid hormone levels. Both hyperthyroidism (overactive thyroid) and, less commonly, hypothyroidism (underactive thyroid) can cause cardiac symptoms, but hyperthyroidism is the classic culprit for palpitations.

The relationship between thyroid function and heart rhythm is so strong that thyroid testing is considered essential in the evaluation of new-onset atrial fibrillation, unexplained tachycardia, or troublesome palpitations.

Hyperthyroidism and palpitations:

Hyperthyroidism (excess thyroid hormone) is a classic cause of palpitations that should always be considered. Thyroid hormones (T3 and T4) directly affect the heart through multiple mechanisms, and even modest thyroid hormone excess produces noticeable cardiovascular effects:

• Direct chronotropic effect: Thyroid hormones increase the firing rate of the sinoatrial node (the heart’s natural pacemaker), directly raising heart rate.
• Increased metabolic demand: Every tissue in the body is working faster, requiring more oxygen delivery, which the heart provides by beating faster.
• Enhanced adrenergic sensitivity: Thyroid hormones increase the heart’s sensitivity to catecholamines (adrenaline, noradrenaline), amplifying the response to any stimulation.
• Increased cardiac contractility: Thyroid hormones increase the force of each heartbeat (positive inotropic effect), making beats feel more forceful and prominent.

Cardiac manifestations of hyperthyroidism include:

• Sinus tachycardia: Resting heart rate is elevated, often 90-120+ beats per minute when normal would be 60-80. The heart beats faster around the clock, including during sleep. This constant tachycardia is exhausting and contributes to fatigue and exercise intolerance.
• Increased contractility: Each beat is more forceful than normal, contributing to the sensation of pounding or throbbing in the chest.
• Atrial fibrillation: Hyperthyroidism significantly increases the risk of AFib — an irregular, often rapid rhythm originating in the atria. AFib occurs in 10-15% of people with hyperthyroidism, much higher than the general population. AFib can cause very noticeable palpitations (often described as fluttering or chaotic beating) and carries a risk of stroke due to blood clots forming in the irregularly contracting atria.
• Other arrhythmias: Increased irritability of cardiac tissue makes various arrhythmias more likely, including premature beats and other supraventricular arrhythmias.
• Widened pulse pressure: The difference between systolic and diastolic blood pressure increases, contributing to the sensation of forceful, bounding heartbeats.
• High-output heart failure: In prolonged or severe hyperthyroidism, the heart may eventually fail from overwork, though this is uncommon.

Characteristics of hyperthyroid-related palpitations:

• Often present at rest, not just with exertion — the heart rate is always elevated
• May be continuous or very frequent rather than episodic
• Heart rate elevated even during sleep (a clue on overnight monitoring)
• Exercise intolerance — heart rate rises excessively with minimal activity and takes a long time to recover
• May feel anxious, nervous, or “wired” even when there’s nothing objective to be anxious about — this is the effect of excess thyroid hormone, not true anxiety
• Palpitations often accompanied by other hyperthyroid symptoms (see below)
• May have visible or palpable thyroid enlargement (goiter)

Other hyperthyroidism symptoms:

Palpitations from hyperthyroidism rarely occur in isolation. Look for these accompanying symptoms:

• Unintentional weight loss despite good or even increased appetite
• Heat intolerance — feeling hot when others are comfortable, excessive sweating
• Fine tremor — a shakiness of the hands that’s noticeable when holding papers or a cup
• Anxiety, nervousness, irritability, emotional lability
• Difficulty sleeping despite fatigue
• Frequent bowel movements or diarrhea
• Muscle weakness, particularly in the thighs (difficulty rising from a chair)
• Menstrual irregularities — lighter or less frequent periods
• Eye changes (specifically in Graves’ disease): bulging eyes, grittiness, redness, irritation, double vision, light sensitivity
• Skin changes: smooth, moist skin; warm to touch
• Hair changes: fine, brittle hair that may fall out
• Shortness of breath, especially with exertion

Subclinical hyperthyroidism:

Even subclinical hyperthyroidism — where TSH is suppressed but T4 and T3 remain in the normal range — is associated with increased heart rate and higher risk of atrial fibrillation. This is particularly relevant in older adults, where subclinical hyperthyroidism may warrant treatment specifically to protect the heart.

Hypothyroidism and palpitations:

While hypothyroidism (underactive thyroid) more commonly causes slow heart rate (bradycardia), it can also cause palpitations through several mechanisms:

• Compensatory tachycardia: In response to the low metabolic state and reduced cardiac output, the heart may compensate with faster beating in some individuals.
• Associated anemia: Hypothyroidism commonly causes mild anemia, which itself causes palpitations through compensatory mechanisms.
• Increased peripheral vascular resistance: Hypothyroidism causes vasoconstriction, which can lead to hypertension and make the heart work harder, potentially causing forceful beats.
• Pericardial effusion: In severe hypothyroidism, fluid can accumulate around the heart, affecting its function.
• Electrolyte effects: Hypothyroidism can affect electrolyte handling.
• Awareness of slow or irregular beats: Some people with hypothyroidism become aware of their slow heart rate or occasional premature beats.

Hypothyroidism is more likely to present with fatigue, weight gain, cold intolerance, and constipation than with palpitations, but the possibility should be considered.

What to test:

TSH (Thyroid-Stimulating Hormone) is the primary screening test for thyroid dysfunction:

• Low TSH (suppressed) suggests hyperthyroidism — the pituitary gland has sensed excess thyroid hormone and backed off its stimulation
• High TSH suggests hypothyroidism — the pituitary is working harder to try to stimulate an underperforming thyroid

Free T4 measures the primary circulating thyroid hormone. Low Free T4 with high TSH confirms overt hypothyroidism; high Free T4 with low TSH confirms overt hyperthyroidism.

Free T3 measures the active form of thyroid hormone. Some hyperthyroid conditions (T3 toxicosis) show elevated T3 with only mildly elevated or normal T4.

TPO antibodies and TSH receptor antibodies (TRAb) can identify autoimmune thyroid disease — Hashimoto’s thyroiditis for hypothyroidism and Graves’ disease for hyperthyroidism.

Anemia: When the Heart Works Harder

Anemia — a deficiency of red blood cells or hemoglobin — is a common and often underappreciated cause of palpitations. The connection is logical: when the blood carries less oxygen, the heart must compensate by beating faster and harder to deliver adequate oxygen to tissues. This compensatory response is exactly what you feel as palpitations.

Anemia affects an estimated 1.6 billion people worldwide, making it one of the most common medical conditions. Many people with anemia don’t realize they have it because symptoms develop gradually as the body adapts. But palpitations — along with fatigue — are often what finally prompts evaluation.

How anemia causes palpitations:

Hemoglobin is the oxygen-carrying protein in red blood cells. When hemoglobin is low, each unit of blood carries less oxygen. The body has remarkable compensatory mechanisms to maintain oxygen delivery:

• Compensatory tachycardia: The heart beats faster to circulate blood more quickly. If each “trip” carries less oxygen, making more trips compensates. Resting heart rate increases, and heart rate rises more than normal with exertion.
• Increased stroke volume: The heart pumps more blood with each beat. This increased stroke volume is what makes each beat feel more forceful and noticeable — the classic pounding sensation.
• Hyperdynamic circulation: Blood flows faster and more turbulently through vessels, which you may perceive as pounding or throbbing, particularly in the neck or head.
• Increased cardiac output: The combination of faster rate and larger stroke volume significantly increases the heart’s workload. The heart is working harder to deliver the same amount of oxygen it normally delivers easily.
• Reduced blood viscosity: Anemic blood is “thinner,” which affects how it flows through the cardiovascular system.

These compensatory mechanisms work remarkably well at rest — many people with moderate anemia feel fine when sitting still. But during exertion, when oxygen demand increases, compensation becomes inadequate. That’s why anemia often presents with palpitations and shortness of breath during activities that used to be easy.

Characteristics of anemia-related palpitations:

• Typically worse with exertion, when oxygen demand increases and the heart has to work even harder
• Associated with fatigue — the most common symptom of anemia and often the most prominent
• May notice heart pounding when climbing stairs, walking uphill, or doing other activities that increase oxygen demand
• Shortness of breath often accompanies palpitations — both result from the heart trying to compensate for reduced oxygen-carrying capacity
• Symptoms typically develop gradually as anemia worsens — the body adapts to slow changes
• Pallor (pale skin) — particularly noticeable in the nail beds, inner eyelids (conjunctivae), and palms; looking in the mirror may not reveal it, but pulling down the lower eyelid shows pale tissue where it should be pink
• Lightheadedness or dizziness, especially when standing up quickly
• May have rapid heartbeat even with minimal exertion
• Cold hands and feet — blood is shunted away from extremities to vital organs
• Exercise intolerance — unable to do what you used to do without symptoms

Common causes of anemia:

Identifying the cause of anemia is essential for treatment:

Iron deficiency anemia: The most common type worldwide. Results from blood loss (heavy menstruation is the most common cause in premenopausal women; GI bleeding from ulcers, polyps, or cancer in older adults), inadequate dietary intake, or poor absorption (celiac disease, gastric bypass surgery, chronic antacid use).

Vitamin B12 deficiency: Causes macrocytic anemia (large red blood cells that don’t function properly). Results from pernicious anemia (autoimmune destruction of intrinsic factor needed for B12 absorption), strict vegan diet without supplementation, gastric surgery, or malabsorption.

Folate deficiency: Also causes macrocytic anemia. Results from inadequate dietary intake, alcoholism, malabsorption, or increased requirements (pregnancy).

Anemia of chronic disease: Associated with chronic infections, inflammatory conditions (rheumatoid arthritis, inflammatory bowel disease), cancer, and kidney disease.

Chronic kidney disease: The kidneys produce erythropoietin (EPO), which stimulates red blood cell production. Kidney disease reduces EPO, causing anemia.

What to test:

Complete Blood Count (CBC) is the essential test for identifying anemia:

• Hemoglobin — the oxygen-carrying protein; low hemoglobin defines anemia
• Hematocrit — the percentage of blood volume made up of red blood cells
• MCV (Mean Corpuscular Volume) — average size of red blood cells; helps classify anemia:
  • Low MCV (microcytic): suggests iron deficiency or thalassemia
  • Normal MCV (normocytic): suggests anemia of chronic disease, acute blood loss, or kidney disease
  • High MCV (macrocytic): suggests B12 or folate deficiency
• Red blood cell count

If anemia is found, additional tests identify the cause:

• Ferritin — reflects iron stores; low ferritin confirms iron deficiency
• Serum iron — iron circulating in blood
• TIBC (Total Iron-Binding Capacity) — elevated in iron deficiency
• Vitamin B12 — for macrocytic anemia
• Folate — for macrocytic anemia
• Reticulocyte count — immature red blood cells; assesses bone marrow response

Electrolyte Imbalances

Electrolytes — particularly potassium, magnesium, and calcium — are essential for normal cardiac electrical activity. The heart’s rhythm depends on the precise movement of these charged particles across cell membranes. When electrolyte levels fall outside the normal range, the heart’s electrical system can malfunction, causing palpitations and potentially dangerous arrhythmias.

Electrolyte imbalances are particularly important to identify because they’re correctable — and because uncorrected, they can progress to more serious rhythm disturbances.

Potassium:

Potassium is perhaps the most critical electrolyte for heart rhythm. Both low potassium (hypokalemia) and high potassium (hyperkalemia) can cause palpitations and arrhythmias:

Hypokalemia (low potassium):

• Increases cardiac irritability and excitability
• Predisposes to premature beats — both PACs and PVCs become more frequent
• Increases risk of atrial fibrillation
• In severe cases, can cause ventricular tachycardia or ventricular fibrillation (life-threatening)
• Makes the heart more sensitive to digoxin toxicity
• Symptoms may include palpitations, muscle weakness, cramps, and fatigue

Common causes of hypokalemia include:

• Diuretics (thiazides, loop diuretics) — a very common cause
• Vomiting and diarrhea
• Excessive sweating
• Inadequate dietary intake
• Certain medications (laxatives, some antibiotics)
• Excessive licorice consumption (yes, really — glycyrrhizin in licorice affects potassium)
• Cushing’s syndrome and other conditions causing excess cortisol

Hyperkalemia (high potassium):

• Slows the heart’s electrical conduction
• Can cause dangerous bradycardia (slow heart rate)
• In severe cases, can cause ventricular fibrillation or cardiac standstill
• More common in kidney disease (kidneys can’t excrete potassium normally)
• Also caused by certain medications — ACE inhibitors, ARBs, potassium-sparing diuretics, NSAIDs
• Can occur with excessive potassium supplementation
• Symptoms may include palpitations, weakness, and potentially no symptoms until a cardiac event

Magnesium:

Magnesium plays a crucial role in stabilizing cardiac electrical activity. It’s involved in over 300 enzymatic reactions in the body, including those controlling heart rhythm. Low magnesium (hypomagnesemia) is common and often overlooked:

• Increases susceptibility to arrhythmias of all types
• Predisposes to premature beats (PACs, PVCs)
• Makes other electrolyte imbalances (particularly potassium) harder to correct — you can’t fully correct hypokalemia without also correcting hypomagnesemia
• Associated with increased risk of atrial fibrillation
• In severe cases, can cause torsades de pointes (a dangerous ventricular arrhythmia)

Causes of low magnesium include:

• Diuretics (both loop and thiazide diuretics increase magnesium loss)
• Proton pump inhibitors (PPIs) — long-term use significantly depletes magnesium
• Alcohol use — alcohol increases urinary magnesium loss
• Malabsorption (inflammatory bowel disease, celiac disease)
• Diabetes — high blood sugar increases urinary magnesium loss
• Inadequate dietary intake
• Chronic diarrhea

Importantly, magnesium deficiency can exist even when serum magnesium levels are normal because most magnesium is stored inside cells, not in the blood. Some people benefit from magnesium supplementation even with “normal” levels.

Calcium:

Calcium affects cardiac muscle contraction and electrical signaling. Abnormal calcium levels alter the heart’s electrical properties:

Hypercalcemia (high calcium):

• Shortens the electrical recovery period of the heart
• Can cause various arrhythmias
• Often causes symptoms like fatigue, confusion, and constipation alongside palpitations
• Usually caused by primary hyperparathyroidism or malignancy

Hypocalcemia (low calcium):

• Prolongs the electrical recovery period
• Can cause palpitations and arrhythmias
• Often accompanied by muscle cramps, numbness, and tingling
• Caused by vitamin D deficiency, parathyroid disorders, or malabsorption

What to test:

Potassium — essential for anyone with palpitations, especially if on diuretics or with kidney disease

Magnesium — often overlooked but important; consider even if level is “normal” but clinical suspicion is high

Calcium — part of comprehensive electrolyte assessment

Sodium — less directly related to palpitations but part of complete electrolyte evaluation

Creatinine and eGFR — kidney function affects electrolyte balance; important context for interpreting results

Blood Sugar Abnormalities

Both low blood sugar (hypoglycemia) and the metabolic effects of diabetes can cause palpitations.

Hypoglycemia:

When blood sugar drops too low, the body releases stress hormones (adrenaline/epinephrine) to mobilize glucose. This adrenaline surge causes:

• Rapid heartbeat (tachycardia)
• Pounding heart
• Sweating
• Tremor
• Anxiety
• Hunger

Hypoglycemia is most common in people taking diabetes medications (insulin, sulfonylureas) but can occur in non-diabetics, particularly with prolonged fasting, after intense exercise, or with certain medical conditions.

Diabetes and palpitations:

Diabetes can cause palpitations through:

• Autonomic neuropathy: Nerve damage affecting heart rate control
• Associated conditions: People with diabetes have higher rates of hypertension, heart disease, and other conditions causing palpitations
• Blood sugar fluctuations: Both high and low sugars affect cardiac function

What to test:

Fasting glucose

HbA1c — reflects average blood sugar over 2-3 months

Other Conditions Causing Palpitations

Dehydration:

Dehydration reduces blood volume, causing the heart to beat faster to maintain blood pressure and circulation. This is why palpitations often occur during illness with fever, vomiting, or diarrhea.

Fever and infection:

Fever increases metabolic rate and heart rate. The heart typically beats about 10 beats per minute faster for each degree (Celsius) of fever.

Pregnancy:

Blood volume increases by 30-50% during pregnancy, and cardiac output rises accordingly. Palpitations are common in pregnancy and usually benign but should still be evaluated.

Anxiety and panic disorder:

Anxiety activates the sympathetic (“fight or flight”) nervous system, increasing heart rate and the force of contractions. Panic attacks characteristically include rapid, pounding heartbeat along with shortness of breath, sweating, and a sense of impending doom. Importantly, anxiety can cause palpitations, and palpitations (from any cause) can cause anxiety — creating a cycle that’s sometimes hard to break.

Medications:

Many medications can cause palpitations:

• Stimulants (ADHD medications, decongestants)
• Asthma medications (beta-agonists like albuterol)
• Thyroid hormone (if dose too high)
• Some antidepressants
• Certain blood pressure medications (can cause reflex tachycardia)
• Caffeine-containing medications

Structural heart disease:

Heart valve problems, cardiomyopathy (weakened heart muscle), and other structural issues can cause palpitations. While not detected by blood tests, cardiac biomarkers may be abnormal:

BNP or NT-proBNP — elevated in heart failure and cardiac strain

Pheochromocytoma:

A rare tumor of the adrenal gland that produces excess adrenaline, causing episodes of severe palpitations, high blood pressure, sweating, and headache. Diagnosed with specific blood or urine tests for catecholamines and metanephrines.

The Testing Strategy for Palpitations

When palpitations are frequent, prolonged, or concerning, blood tests help identify underlying metabolic and hormonal causes.

Core tests for unexplained palpitations:

Thyroid function (essential):

• TSH
• Free T4 (if TSH abnormal)

Complete blood count:

• CBC — screens for anemia

Electrolytes:

• Potassium
• Magnesium
• Calcium

Metabolic:

• Fasting glucose

Additional tests based on clinical picture:

• If anemia found: ferritin, iron, TIBC, B12, folate
• If heart failure suspected: BNP or NT-proBNP
• If thyroid dysfunction confirmed: TPO antibodies, Free T3
• If pheochromocytoma suspected: plasma metanephrines
• Creatinine — kidney function affects electrolytes

Other diagnostic tests (not blood tests):

Blood tests identify metabolic causes but don’t directly diagnose arrhythmias. Other tests include:

• ECG (electrocardiogram): Records heart’s electrical activity; may capture arrhythmia if occurring during the test
• Holter monitor: Continuous ECG recording for 24-48 hours
• Event monitor: Worn for weeks; records when you activate it during symptoms
• Echocardiogram: Ultrasound of the heart to assess structure and function

What to Do With the Results

If hyperthyroidism is found:

Treatment of hyperthyroidism (with medications, radioactive iodine, or surgery depending on the cause and severity) typically resolves palpitations. Heart rate normalizes as thyroid levels normalize, and the risk of atrial fibrillation decreases. If AFib has developed, it may or may not resolve with thyroid treatment — some people require additional cardiac treatment.

If anemia is found:

Treating the underlying cause of anemia (iron supplementation for iron deficiency, B12 injections for B12 deficiency, etc.) allows the heart to return to normal function. As hemoglobin rises, the heart no longer needs to work as hard, and palpitations resolve.

If electrolyte imbalances are found:

Correcting potassium, magnesium, or calcium levels typically improves cardiac symptoms. If the imbalance is medication-induced (e.g., from diuretics), medication adjustments or supplementation may be needed. Identifying and addressing the underlying cause prevents recurrence.

If blood sugar abnormalities are found:

Managing blood sugar — whether treating hypoglycemic episodes or achieving better overall diabetes control — can reduce palpitations. For hypoglycemia, identifying triggers and adjusting diet or medications helps prevent episodes.

When Tests Are Normal

Normal blood tests rule out many metabolic causes of palpitations — thyroid dysfunction, anemia, electrolyte imbalances, blood sugar abnormalities — but don’t mean the palpitations aren’t real or that nothing is wrong. They simply narrow the differential diagnosis and redirect attention to other possibilities.

If blood tests are normal but palpitations continue, consider:

• Benign premature beats (PACs, PVCs): Premature atrial contractions and premature ventricular contractions are extremely common — virtually everyone has some. They’re usually harmless but can be very noticeable and bothersome. PACs and PVCs are often exacerbated by caffeine, alcohol, stress, lack of sleep, and certain medications. Management typically involves lifestyle modification (reducing triggers) and reassurance. If very frequent or symptomatic, medications or ablation procedures are sometimes used.
• Anxiety and stress: The sympathetic nervous system activates the “fight or flight” response, releasing adrenaline and increasing heart rate and contractility. Anxiety can cause very real cardiac symptoms — racing heart, pounding, chest tightness — even when the heart rhythm is completely normal. Panic attacks are characterized by sudden-onset palpitations along with shortness of breath, sweating, and a sense of impending doom. Treatment may include stress reduction techniques, cognitive behavioral therapy, and sometimes medication. Importantly, anxiety can cause palpitations, and palpitations (from any cause) can cause anxiety — creating a self-perpetuating cycle that sometimes requires addressing both aspects.
• Caffeine, alcohol, and other substances: These can cause palpitations even when blood tests are normal. A trial of eliminating caffeine (coffee, tea, energy drinks, chocolate) for 2-3 weeks often reveals whether it’s a significant contributor. Reducing or eliminating alcohol helps many people.
• Paroxysmal arrhythmias: Some arrhythmias occur intermittently (paroxysmal atrial fibrillation, SVT) and may not be present during a standard ECG. Extended monitoring — 24-48 hour Holter monitor, 1-2 week event monitor, or even longer-term patch monitors or implantable loop recorders — may be needed to capture what’s happening during symptomatic episodes. The key is correlating symptoms with the heart rhythm at that moment.
• Structural heart disease: Heart valve problems (mitral valve prolapse, aortic stenosis), cardiomyopathy (weakened or thickened heart muscle), and other structural abnormalities can cause palpitations. These are evaluated with echocardiogram (heart ultrasound), not blood tests.
• Supraventricular tachycardia (SVT): A category of arrhythmias that cause sudden-onset episodes of very rapid heartbeat (often 150-250 bpm), sometimes with abrupt onset and offset. May require electrophysiology study for definitive diagnosis and can be cured with catheter ablation.
• Postural orthostatic tachycardia syndrome (POTS): Causes excessive increase in heart rate upon standing, along with lightheadedness and other symptoms. Diagnosed with tilt-table testing or active standing test. More common in young women.
• Inappropriate sinus tachycardia: Resting heart rate is elevated without an identifiable cause. The heart rhythm is normal (sinus rhythm), just persistently faster than it should be.
• Deconditioning: Sedentary lifestyle leads to reduced cardiovascular fitness, causing the heart rate to rise more than normal with minimal exertion. Regular aerobic exercise can improve this over time.

If blood tests are normal and palpitations are concerning, the next step is typically some form of cardiac monitoring to correlate symptoms with heart rhythm. The goal is to capture what your heart is doing when you feel palpitations — this determines whether the rhythm is normal (and reassurance is appropriate) or abnormal (and specific treatment is needed).

Lifestyle Approaches

While investigating underlying causes, these strategies can help reduce palpitations:

• Reduce or eliminate caffeine: Coffee, tea, energy drinks, chocolate, and caffeinated medications
• Limit alcohol: Even moderate amounts can trigger palpitations in susceptible individuals
• Quit smoking: Nicotine is a stimulant that affects heart rhythm
• Stay hydrated: Dehydration can trigger palpitations
• Get adequate sleep: Sleep deprivation increases susceptibility to palpitations
• Manage stress: Stress reduction techniques, meditation, yoga, and regular exercise can all help
• Review medications and supplements: Discuss with your healthcare provider; some may need adjustment
• Vagal maneuvers: Techniques like bearing down or splashing cold water on the face can sometimes interrupt certain arrhythmias
• Identify and avoid personal triggers: Keep a symptom diary to identify patterns

The Bottom Line

Heart palpitations are extremely common and most are benign — but they can also signal underlying conditions that benefit from identification and treatment. The key is distinguishing concerning palpitations (frequent, prolonged, associated with other symptoms) from benign ones (occasional, brief, clearly triggered by caffeine or stress).

Blood tests play a crucial role in evaluating palpitations by identifying metabolic and hormonal causes:

• Thyroid dysfunction — particularly hyperthyroidism — is one of the most important causes to identify. It’s common (affecting 1-2% of the population), causes significant cardiac effects including increased risk of atrial fibrillation, and is very treatable. A simple TSH test is the essential first step.
• Anemia causes the heart to work overtime to compensate for reduced oxygen-carrying capacity. Treating the underlying cause of anemia allows the heart to return to normal function and resolves palpitations.
• Electrolyte imbalances — especially potassium, magnesium, and calcium — directly affect the heart’s electrical system. Identifying and correcting imbalances can prevent palpitations and potentially dangerous arrhythmias.
• Blood sugar abnormalities can cause palpitations through adrenaline release (hypoglycemia) or autonomic effects (diabetes).

Don’t ignore persistent or concerning palpitations. While many are benign, evaluation often uncovers treatable conditions. The good news is that many causes of palpitations — thyroid disorders, anemia, electrolyte imbalances — are readily correctable, and treatment can eliminate symptoms entirely.

At the same time, don’t panic about occasional palpitations. If you feel a skipped beat or brief flutter after your third cup of coffee, the explanation is obvious and the solution is simple. But if palpitations are frequent, prolonged, or accompanied by other symptoms, get them evaluated.

Blood tests are just one part of palpitation evaluation. If blood tests are normal but palpitations continue, cardiac monitoring (Holter monitor, event recorder) may be needed to capture what’s happening during episodes. The goal is to understand what your heart is doing during palpitations so appropriate management can be determined.

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Key Takeaways

• Heart palpitations are extremely common — affecting up to 16% of people at some point — and most are benign, but investigation is warranted for frequent, prolonged, or concerning episodes
• Thyroid dysfunction is a major, treatable cause — hyperthyroidism classically causes palpitations and significantly increases the risk of atrial fibrillation; a simple TSH test can identify this; treatment normalizes heart rhythm in most cases
• Anemia causes the heart to compensate — beating faster and harder to make up for reduced oxygen-carrying capacity; treating the underlying cause of anemia resolves palpitations as hemoglobin normalizes
• Electrolyte imbalances (potassium, magnesium, calcium) directly affect the heart’s electrical system and can cause arrhythmias; these are readily correctable once identified
• Blood sugar abnormalities — both hypoglycemia (through adrenaline release) and diabetes (through autonomic effects) — can cause palpitations
• Lifestyle factors matter significantly — caffeine, alcohol, nicotine, stress, sleep deprivation, and dehydration all affect heart rhythm; modifying these can substantially reduce palpitations
• Warning signs require prompt attention — palpitations with chest pain, fainting, severe shortness of breath, or prolonged rapid heartbeat need immediate evaluation
• Normal blood tests don’t rule out all causes — if metabolic causes are excluded, cardiac monitoring (Holter, event monitor) may be needed to capture and diagnose intermittent arrhythmias
• Many palpitations are benign premature beats — PACs and PVCs are extremely common and usually harmless; reassurance and lifestyle modification are often sufficient
• The goal is to understand what your heart is doing — blood tests identify metabolic causes, while cardiac monitoring identifies rhythm disturbances; together they provide a complete picture