What should you know about passing out from exhaustion?

Fainting occurs when the brain briefly receives too little blood flow. Heat, prolonged exertion, dehydration, not eating, pain, or a sudden drop in blood pressure can contribute. Exhaustion may also accompany an illness such as anaemia, COVID-19, or chronic kidney disease. Ongoing fatigue without a true loss of consciousness can have different causes, including burnout, coeliac disease, alcohol use disorder, or chronic fatigue syndrome. The event itself does not identify one diagnosis.

If someone faints, place them flat on their back and raise their legs if there is no injury or breathing problem. Loosen tight clothing, check breathing, and keep them away from heat. Do not give food or drink until they are fully alert. Arrange a medical review for a first, unexplained, or repeated episode; record what happened before it, how long recovery took, recent exertion, fluids, food, medicines, and any illness.

Call emergency services if the person does not wake promptly, has trouble breathing, chest pain, a severe headache, a seizure, new weakness, confusion, a serious injury, or faints during exercise. Urgent assessment is also needed for palpitations, ongoing vomiting, signs of severe dehydration, or repeated fainting. Do not let someone who remains dizzy drive.

Ask whether you need blood pressure checks lying and standing, an ECG, blood tests, or a review of medicines. Mention family history of fainting or sudden cardiac death and any warning symptoms before you lost consciousness.