What should you know about heart suddenly racing?

You may feel pounding, fluttering or a fast pulse in your chest, neck or throat. Common triggers include exercise, fear, poor sleep, fever, caffeine, nicotine and some medicines. Dehydration or low blood sugar can also make the heart beat faster. Anaemia, iron deficiency anaemia, an overactive thyroid and an abnormal rhythm such as atrial fibrillation are possible medical causes. A racing heartbeat is a symptom, so it does not by itself identify the cause.

Note when it started, whether it began and stopped suddenly, how long it lasted, and whether the rhythm felt regular or uneven. Breathlessness, chest discomfort, fainting, marked weakness or new confusion make the episode more concerning.

Stop strenuous activity and sit somewhere safe. Breathe slowly and steadily, loosen tight clothing, and sip water if you can drink normally. Avoid caffeine, nicotine, energy drinks and decongestants until you understand the trigger. Do not take someone else’s heart medicine. Arrange a clinical review if episodes recur, last longer than expected, happen at rest, or interfere with daily activities; a clinician may check your pulse, blood pressure, blood count, thyroid function and heart rhythm.

Seek emergency help for a racing heartbeat with chest pain or pressure, severe breathing difficulty, fainting, collapse, blue or grey lips, or sudden one-sided weakness or trouble speaking. Get urgent advice if the heartbeat remains very fast at rest, feels markedly irregular, or you feel light-headed and unsafe. Do not drive yourself if you might faint.

Ask whether your symptoms could be related to a medicine, thyroid problem, anaemia, dehydration or an abnormal rhythm. Ask whether you need an ECG or blood tests, what symptoms should trigger emergency care, and how to record your pulse and episode details.