Heart racing at rest: what should you know?

Rest removes exercise as an obvious explanation, but the body can still release stress hormones. Fever, dehydration, anaemia, low blood sugar, nicotine, caffeine, and some inhalers or decongestants can also affect pulse.

A fast, uneven rhythm may be atrial fibrillation or another rhythm disturbance. Hyperthyroidism can increase heart rate and may also cause heat intolerance, shaking, or weight change. Heart failure is more often associated with breathlessness, swelling, and reduced exercise tolerance.

Sit upright, rest, and check whether the sensation feels regular or uneven. Take small sips of water unless a clinician has told you to restrict fluids. Review recent caffeine, nicotine, alcohol, medicines, illness, and missed meals.

Do not take someone else's heart medicine or try forceful manoeuvres to slow the beat. Note the start and end of the episode, and arrange a review when symptoms recur, last longer than expected, or disturb sleep.

Call emergency services if a racing heartbeat comes with chest pain, severe breathlessness, fainting, new weakness, confusion, or a cold, clammy feeling. Get help rather than travelling alone if you feel unsteady.

Seek same-day advice for a sustained fast or irregular pulse, especially with dizziness, fever, vomiting, or known heart disease. A clinician can examine you and consider an electrocardiogram, monitoring, and blood tests.

Ask whether your pulse pattern needs monitoring, whether any medicine or supplement could be contributing, and what symptoms should send you directly to emergency care.