Waking up with a racing heart: causes, red flags and when to get it checked

At night and early morning, hormones such as cortisol rise and the nervous system shifts, making you more aware of the heartbeat. A surge of adrenaline from a dream, anxiety, apnoea or alcohol wearing off can cause a rapid pulse. An arrhythmia is possible, so a documented rhythm is the most important step.

• Anxiety, panic attacks and vivid dreams or nightmares, often with a feeling of dread.

• Alcohol the night before: heart rate rises as it wears off in the early hours.

• Caffeine, nicotine and stimulant medicines or energy drinks late in the day.

• Obstructive sleep apnoea: snoring, gasping, and waking with a pounding heart and dry mouth.

• Perimenopause and menopause: hot flushes and night sweats with palpitations.

• Overactive thyroid, anaemia and low blood sugar.

• Atrial fibrillation and other arrhythmias, including supraventricular tachycardia, with sudden starts and stops.

• Structural heart disease and electrolyte disturbances, which are less common.

Palpitations with chest pain, fainting or near-fainting, severe breathlessness, an irregularly irregular pulse, a very fast pulse that is sustained, or a family history of sudden cardiac death or inherited heart conditions warrant urgent attention.

• Call 999: palpitations with chest pain, collapse, severe breathlessness or confusion.

• Same-day GP or NHS 111: a fast heartbeat that persists or is accompanied by dizziness.

• GP within a week or two: recurrent night palpitations, irregular pulse or snoring with daytime sleepiness.

• Routine: occasional racing heart after alcohol or caffeine that settles quickly.

Doctors ask how often, how long, how it starts and stops, whether regular, associated symptoms, caffeine, alcohol, medicines, drugs, thyroid symptoms, snoring and family history. They check pulse, blood pressure, heart sounds and thyroid signs and arrange an ECG.

• Resting 12-lead ECG: looks for rhythm and conduction abnormalities.

• Blood tests: full blood count, thyroid function, electrolytes and glucose.

• Ambulatory ECG monitoring (24-hour to 7-day patch or event recorder): to capture an episode.

• Echocardiogram: for structural heart disease.

• Sleep study: if sleep apnoea is suspected.

Cut back caffeine and alcohol, especially in the evening, keep regular sleep times and practise relaxation techniques. When an episode starts, sit, breathe slowly, and count your pulse for a minute noting whether it is regular. Vagal manoeuvres such as bearing down can stop some supraventricular tachycardias if advised by a doctor.

The NHS route is a GP, ECG and monitoring through cardiology. Private cardiology offers rapid ECG, event monitors and echocardiography directly.