Why does anaemia cause fainting?

Fainting, also called syncope, is a brief loss of consciousness caused by a temporary reduction in brain blood flow. Before it happens, some people notice dizziness, nausea, sweating, blurred vision, ringing in the ears, or a sense of warmth. Standing still, getting up quickly, dehydration, pain, or exertion can make an episode more likely in someone who is already unwell.

Fainting is a common presentation of Anaemia. A blackout can also have heart, neurological, blood-pressure, medication, or blood-sugar causes, so it should not be attributed to anaemia without an assessment.

If warning symptoms begin, sit or lie flat at once and raise your legs if you can do so safely. Loosen tight clothing and ask someone to stay with you. When the feeling passes, get up gradually and avoid driving, swimming alone, heights, or machinery until you have been assessed.

Arrange medical review after any new fainting episode, even if you recover quickly. A clinician may ask about triggers, duration, injuries, chest symptoms, bleeding, medicines, and previous anaemia before deciding on blood tests, heart checks, or other investigations.

Call emergency services if someone does not wake promptly, has chest pain, severe breathlessness, a seizure, new weakness, trouble speaking, a serious injury, or faints during exercise. Seek urgent assessment for fainting with a fast or irregular heartbeat.

Urgent care is also needed if you have black stools, vomiting blood, heavy bleeding, or repeated episodes. Do not drive yourself to obtain help after a blackout.

Ask whether the event sounds like fainting, whether anaemia may be contributing, what could be causing any anaemia, and which warning signs mean you should seek help immediately. If possible, bring an eyewitness account of what happened.