Laboratory Tests for Palpitations
Order a complete blood count, comprehensive metabolic panel (including electrolytes, renal function, and glucose), thyroid-stimulating hormone, and a 12-lead ECG as the core initial workup for all patients presenting with palpitations. 1, 2
Core Laboratory Panel
The essential laboratory tests for evaluating palpitations include:
Complete blood count (CBC): Identifies anemia (which can cause compensatory tachycardia and palpitations), polycythemia, or infection 1, 2
Comprehensive metabolic panel: Assesses electrolyte disturbances (particularly potassium, calcium, magnesium), renal function (creatinine, eGFR), and glucose abnormalities—all of which can trigger arrhythmias 1, 2
Thyroid-stimulating hormone (TSH): Hyperthyroidism is a common and treatable cause of palpitations, and thyroid dysfunction affects cardiac rhythm and response to medications like digoxin 1, 3
Fasting glucose or hemoglobin A1c: Diabetes and glucose abnormalities are associated with cardiovascular disease and arrhythmias 1
Liver function tests: Provide baseline data and identify hepatic dysfunction that may affect medication metabolism 1
Lipid profile: Assesses cardiovascular risk factors 1
Additional Tests Based on Clinical Context
For women of childbearing potential: Obtain a pregnancy test, as pregnancy is a physiologic state that commonly causes palpitations and alters management decisions 1
For patients on digoxin: Measure digoxin level, as toxicity commonly presents with palpitations and arrhythmias 1, 3
When substance use is suspected: Order urine toxicology screen for stimulants (cocaine, amphetamines) and blood alcohol level, as these are common causes of palpitations in certain populations 2
When pheochromocytoma is suspected (episodic palpitations with pallor, sweating, headache, hypertension): Obtain plasma metanephrines or 24-hour urinary metanephrines 1
When Cushing's syndrome is suspected (central obesity, facial rounding, easy bruising, hypertension): Measure serum cortisol with ACTH 1
Electrocardiographic Evaluation
A 12-lead ECG is mandatory at the initial encounter to identify arrhythmias, conduction abnormalities, structural heart disease, or ischemia 1
Prolonged ECG monitoring (Holter monitor, event recorder, or implantable loop recorder) is indicated when palpitations are recurrent and the initial ECG is non-diagnostic 1
Cardiac Testing When Indicated
Echocardiography is recommended as a first evaluation step when palpitations are associated with syncope, chest pain, or when structural heart disease is suspected 1
Cardiac biomarkers (troponin) should be obtained if there is concern for myocardial ischemia or infarction 1
Common Pitfalls to Avoid
Do not skip TSH testing: Thyroid dysfunction is frequently missed and is a highly treatable cause of palpitations 1, 3
Do not forget pregnancy testing in women of childbearing age: Pregnancy dramatically alters the differential diagnosis and management 1
Do not overlook electrolytes: Hypokalemia, hypomagnesemia, and hypocalcemia are common, correctable causes of arrhythmias 1
Do not delay ECG: The 12-lead ECG should be performed immediately, as it may reveal life-threatening arrhythmias requiring urgent intervention 1
Diagnostic Approach
The history and physical examination combined with the core laboratory panel and ECG determine the etiology in approximately 40% of patients with palpitations 2. When the initial evaluation suggests cardiac disease (abnormal ECG, structural heart disease, syncope with palpitations), proceed immediately to echocardiography and prolonged ECG monitoring 1. When psychiatric illness is suspected (multiple somatic complaints, anxiety, stress), consider psychiatric assessment after excluding cardiac and metabolic causes 1, 2.