Heart racing when you lie down: what should you know?

When the room is quiet and your body is still, normal beats may feel stronger than they did during the day. Lying down after a late meal, alcohol, caffeine, nicotine, stress, or poor sleep can make the sensation more noticeable. Dehydration, anaemia, thyroid overactivity, low blood sugar, and anxiety can also contribute. An irregular rhythm such as atrial fibrillation is another possibility. Breathlessness when lying flat, waking short of breath, or new ankle swelling deserves particular attention because it may indicate a circulation or heart problem.

Sit up slowly and see whether the sensation settles; do not repeatedly change position if you feel faint. Note whether the rhythm feels steady or uneven, when it starts, how long it lasts, and whether it follows food, exercise, alcohol, caffeine, or a stressful thought. Hydrate normally and keep a regular sleep routine. Avoid taking someone else’s heart medicine or using supplements to slow the pulse. Arrange a medical review when symptoms recur, disturb sleep, or are accompanied by breathlessness or dizziness.

Call emergency services for palpitations with chest pain, severe breathlessness, fainting, confusion, or a sustained very fast or irregular pulse. Seek prompt advice if you cannot lie flat because of breathing difficulty, develop new swelling, or have repeated nighttime episodes. These symptoms need assessment rather than reassurance based only on position.

Ask whether you need an ECG or a period of heart monitoring, and whether blood tests could check anaemia or thyroid function. Tell the clinician about sleep symptoms, snoring, medicines, supplements, caffeine, alcohol, and any family history of rhythm problems.