Heart keeps racing: possible causes and next steps

Palpitations may follow exercise, stress, poor sleep, fever, caffeine, nicotine, or some medicines. Dehydration and hypoglycaemia can also make the heart feel fast, often alongside thirst, shakiness, sweating, or weakness. Anaemia, iron deficiency anaemia, and hyperthyroidism may cause repeated racing with tiredness, breathlessness, heat intolerance, or weight change. An irregular rhythm such as atrial fibrillation is another possibility. Heart failure can be associated with breathlessness, swelling, or reduced exercise tolerance, but a racing sensation alone does not establish its cause.

During an episode, check whether the beat feels steady or uneven, what you were doing, and whether it stops after rest. A pulse reading can be useful if available, but do not delay urgent care to measure it.

Stop strenuous activity and sit somewhere safe. Breathe slowly, drink water if you can, and avoid caffeine, nicotine, and alcohol while symptoms continue. Do not take someone else’s heart medicine. Book a medical review if episodes recur, last longer than expected, begin without an obvious trigger, or interfere with sleep or activity. Assessment may include a pulse check, ECG, blood tests, or a wearable monitor.

Call emergency services for a racing heart with chest pain, severe breathlessness, fainting, confusion, or sudden weakness. Seek urgent assessment if the rhythm remains very fast or irregular, particularly when you feel unwell. Arrange non-emergency review for recurrent episodes, new symptoms after starting a medicine, or palpitations with fatigue, tremor, thirst, or swelling.

Could my symptoms reflect an irregular rhythm or a medical trigger? Would an ECG or longer monitoring help? Should I have blood tests for anaemia, thyroid problems, or glucose? Which activities and medicines should I avoid during an episode?