What should you know about fainting often?

Fainting, also called syncope, is a brief loss of consciousness caused by reduced blood flow to the brain. People may feel warm, sweaty, nauseated, light-headed or have blurred vision beforehand, although an episode can happen suddenly.

Common triggers include standing for a long time, heat, pain, fear, not drinking enough and not eating. Anaemia can present with light-headedness or fainting, while dehydration and hypoglycaemia can also contribute. Atrial fibrillation and other heart rhythm problems may present with fainting or a racing, irregular heartbeat, so recurrent episodes deserve a proper review.

A clinician may ask what you were doing, whether you had warning symptoms, how long you were unresponsive and whether anyone saw shaking or injury. They may check blood pressure, heart rate and an electrocardiogram, with further tests guided by your history.

If you feel faint, lie down and raise your legs if possible. If lying down is not safe, sit with your head lowered between your knees. Loosen tight clothing, move away from heat and ask someone to stay with you. Do not stand up quickly after the feeling passes.

Record what happened, including your position, food and fluid intake, warning symptoms, medicines and any palpitations. Until you have been assessed, take care around driving, heights, open water and machinery. Do not stop prescribed medicine without discussing it with a clinician.

Call emergency services if someone does not wake promptly, is not breathing normally, has chest pain, severe shortness of breath, a new weakness, trouble speaking, a severe headache or a serious injury. Seek urgent assessment when fainting happens during exercise, while lying down, with strong palpitations, or without any warning.

Even when you recover quickly, book a prompt appointment if fainting has happened repeatedly, is becoming more frequent, or occurs with bleeding, marked tiredness, persistent vomiting or poor fluid intake. Bring a witness if possible, because their description can help distinguish fainting from a seizure or another cause.

Ask: Could my symptoms be related to blood pressure, heart rhythm, anaemia, dehydration or low blood sugar? Do I need an electrocardiogram or blood tests? Which activities should I avoid until the cause is clearer? What should someone with me do if I faint again?