Difference between shock and fainting

Fainting may follow standing for a long time, heat, pain, fear or a sudden drop in blood pressure. A person often becomes pale, sweaty or light-headed, loses consciousness briefly and then recovers. Shock can follow severe bleeding, a serious infection, a major allergic reaction or another emergency. Signs can include cold clammy skin, confusion, fast breathing, a weak pulse and worsening drowsiness.

A faint can sometimes signal an underlying problem such as anaemia, dehydration, hypoglycaemia or an abnormal heart rhythm. The event should be assessed if it is unexplained, repeated or associated with injury.

If someone feels faint, help them lie flat and raise their legs if there is no injury or breathing problem. Check that they are breathing normally and loosen tight clothing. If they do not recover promptly, are injured, or seem seriously unwell, call emergency services. For suspected shock, keep the person lying down, keep them warm, do not give food or drink, and seek emergency help immediately.

Treat collapse with chest pain, severe breathlessness, seizure-like movements, heavy bleeding, confusion, a severe allergic reaction or a very irregular heartbeat as an emergency. Urgent assessment is also needed after a head injury, during pregnancy, or when fainting occurs during exercise.

Tell the clinician what happened before, during and after the event, including posture, warning symptoms, recovery time, injury, medicines and food or fluid intake. Ask whether blood tests, heart monitoring or review of conditions such as atrial fibrillation is appropriate.