What should you know about blacking out causes?

Fainting may happen after standing still, standing quickly, heat, pain, fear, or not eating or drinking enough. Some people notice warning signs such as nausea, sweating, blurred vision, ringing in the ears, or warmth. Anaemia can reduce oxygen delivery and contribute to light-headedness. Dehydration lowers circulating fluid, while Hypoglycaemia means blood sugar has fallen too low. Atrial Fibrillation and other rhythm disturbances can affect how efficiently the heart fills and pumps.

A clinician will want to know what happened before the episode, how long recovery took, whether you were injured, and whether anyone saw shaking or unusual movements. A blackout during exertion, without warning, or while lying down has a different level of concern from a faint after prolonged standing.

Lie flat with your legs raised if possible, loosen tight clothing, and stay still until you feel fully recovered. Do not get up quickly or drive until the cause has been assessed. Drink fluids when you are alert and able to swallow, and eat a snack if you may have missed a meal, unless a clinician has given different instructions. Arrange a medical review after an unexplained blackout, even if you feel normal again.

Call emergency services if the person does not wake promptly, has trouble breathing, chest pain, a severe headache, new weakness, confusion, a serious injury, or repeated episodes. Seek urgent assessment for fainting during exercise, palpitations, or a family history of sudden cardiac death. Do not put food or drink into the mouth of someone who is unconscious.

Ask whether you need a heart rhythm check, blood tests for anaemia or glucose, and a review of hydration, meals, and medicines. Bring a witness's description, including your posture, warning symptoms, skin colour, movements, and recovery.