Fast Heart Rate

A resting heart rate above 100 beats per minute in adults is generally classified as tachycardia (a fast heart rate), though what's "normal" varies by individual, fitness level, and circumstance.

Common, Non-Dangerous Causes

Exercise, stress or anxiety, caffeine, dehydration, fever, and certain medications (including some decongestants and asthma inhalers) commonly cause a temporary increase in heart rate that resolves once the trigger passes.

Medical Causes

A persistently or unexplained fast heart rate can be linked to an overactive thyroid (hyperthyroidism), anemia, a heart rhythm disorder (arrhythmia) such as atrial fibrillation or supraventricular tachycardia, or, less commonly, an underlying heart condition.

How It Relates to Palpitations

A fast heart rate often — but not always — comes with the sensation of palpitations; it's also possible to have a measurably fast heart rate without feeling it at all, which is one reason unexplained tachycardia found incidentally is still worth investigating.

When to See a Doctor

See a doctor if a fast heart rate happens frequently without an obvious trigger, doesn't settle down after resting, or comes with chest pain, shortness of breath, dizziness, or fainting — the last group needs emergency evaluation.