Headache and passing out

Passing out happens when the brain briefly receives less blood flow. Standing quickly, prolonged standing, pain, fear, dehydration, heat exhaustion, or not eating can trigger it. A viral illness such as a common cold or COVID-19 may leave you weak, while dengue fever can cause headache and significant illness. Allergic rhinitis, chronic sinusitis, and anxiety can contribute to discomfort or light-headedness, but they do not explain every fainting episode.

If you feel faint, lie down safely and raise your legs if possible. Loosen tight clothing, move away from heat, and ask someone to stay with you. Once fully alert, take small sips of fluid and eat if you can swallow safely. Do not drive, climb, or return to strenuous activity until the cause has been assessed, particularly after an unexplained episode.

Call emergency services if the person does not wake promptly, has trouble breathing, chest pain, an irregular heartbeat, seizure-like movements, severe sudden headache, confusion, weakness, speech trouble, or a serious injury. Prompt medical review is needed after a first faint, repeated episodes, fainting during exercise, pregnancy, or fainting with fever, bleeding, or ongoing vomiting.

Describe what you were doing, your posture, warning sensations, food and fluid intake, medicines, illness, injuries, and how quickly you recovered. Ask whether blood pressure, heart rhythm, blood tests, or further assessment may help identify the trigger.