My heart is racing and I feel dizzy

Palpitations may happen after exertion, stress, poor sleep, caffeine, fever, or some medicines. Dizziness can occur when blood pressure or blood sugar falls, or when the heart is not pumping in a steady pattern. Dehydration, anaemia, an overactive thyroid, and an irregular rhythm such as atrial fibrillation are possible causes; these symptoms alone cannot identify one diagnosis.

Note when the sensation began, how long each episode lasts, whether the rhythm feels regular or uneven, and what you were doing. A clinician may check your pulse, blood pressure, an electrocardiogram, and blood tests.

Stop strenuous activity and sit or lie down somewhere safe. Do not drive while dizzy. Sip water if you can drink normally, and avoid caffeine, nicotine, alcohol, and non-prescribed stimulants until you have advice. If you have diabetes, check your glucose and follow your personal low-glucose plan.

Arrange a medical assessment, especially if this is new, keeps returning, or occurs with weakness, breathlessness, or swelling. Bring a list of medicines and supplements, including anything recently started.

Call emergency services if the racing heartbeat does not settle and you have chest pressure, severe shortness of breath, fainting, confusion, or new weakness on one side. Seek same-day medical care for repeated episodes, persistent dizziness, or a very fast or irregular pulse. Even if symptoms stop, a first episode deserves clinical review.

Could a heart rhythm, thyroid problem, anaemia, dehydration, or glucose change explain this? Do I need an electrocardiogram or monitoring? Which medicines, drinks, or supplements should I avoid, and what should I do if it happens again?