Pre-syncope — the sensation that you are about to faint — happens when the brain briefly gets less blood flow. Common triggers include dehydration, skipping meals, hot environments, standing up too fast, prolonged standing, pain, anxiety, and certain medicines. Most episodes are harmless and pass quickly if you sit or lie down and raise your legs.
See a doctor if you have repeated episodes, if they happen during exertion, or if you actually lose consciousness. Fainting can sometimes relate to anemia, heart-rhythm disturbances, or blood-pressure issues that benefit from assessment.
Call your local emergency number if fainting comes with chest pain, palpitations, severe breathlessness, a severe headache, slurred speech or one-sided weakness, or if someone faints and does not quickly come round. Fainting during exercise should always be checked promptly. This is general information only.