What should you know about fainting from shock?

A strong reaction may widen blood vessels and slow the heart briefly. Blood pressure then falls, causing light-headedness or loss of consciousness. Warning signs can include sweating, nausea, warmth, blurred vision, or ringing in the ears. The episode is often brief, but the trigger should not be assumed to be the only explanation, especially after an injury or in someone with heart symptoms. Dehydration, anaemia, low blood sugar, or an irregular rhythm such as atrial fibrillation can also contribute.

Help the person lie flat and raise their legs if there is no suspected injury. Loosen tight clothing, keep the area calm, and check that they are breathing normally. Do not give food, drink, or tablets while they are unconscious. Once fully alert, let them sit up slowly and remain with them. Record what happened before the collapse, how long recovery took, and any shaking, injury, chest discomfort, or palpitations.

Call emergency services if the person does not wake promptly, is not breathing normally, has chest pain, severe breathlessness, a new neurological problem, heavy bleeding, or a serious injury. Arrange medical assessment after a first faint, repeated episodes, fainting during exercise, or an episode without a clear emotional trigger. Do not drive until a clinician has advised you.

Could medicines, dehydration, anaemia, blood sugar, or heart rhythm have contributed? Do I need an examination, blood tests, or an electrocardiogram? What warning signs should prompt urgent help if it happens again?