Heart racing when waking up

A faster heartbeat can be a normal response to waking suddenly, anxiety, a nightmare, illness, caffeine, alcohol, or some medicines. Dehydration and hypoglycaemia can also make the heart beat faster. Anaemia, iron deficiency anaemia, an overactive thyroid, or atrial fibrillation may cause repeated palpitations, sometimes with tiredness, breathlessness, tremor, or an uneven rhythm. These symptoms do not identify one cause by themselves.

Sit upright, breathe slowly, and notice whether the sensation settles after a few minutes. Avoid driving while dizzy. Record when it starts, how long it lasts, whether the rhythm feels regular, and any triggers such as poor sleep, missed food, caffeine, or new medicine. Arrange a clinical review if episodes recur, disturb sleep, or occur with fatigue or breathlessness.

Seek emergency help for palpitations with chest pain, severe breathlessness, fainting, confusion, or persistent marked dizziness. Urgent assessment is also appropriate when a fast or irregular heartbeat does not settle, particularly if you have known heart disease. A clinician may check your pulse, blood pressure, an electrocardiogram, blood count, thyroid function, and glucose.

Ask whether your symptoms suggest a rhythm disturbance, anaemia, thyroid problem, or a medication effect; ask which recordings to bring and whether testing is needed during an episode.