High blood pressure and passing out: what to know

Fainting happens when the brain temporarily receives less blood flow. It can follow dehydration, overheating, prolonged standing, pain, emotional stress, a sudden drop in blood pressure, or a heart rhythm problem. Blood pressure medicine can sometimes contribute if the dose or combination is not right for you. A high reading taken after the event may reflect fear, pain, or exertion rather than the reason you fainted.

The circumstances matter: whether you had warning symptoms, were exercising, injured yourself, felt a racing heartbeat, or recovered quickly. A clinician may review your heart rhythm, medicines, hydration, and blood pressure in different positions.

Lay the person flat and raise the legs if there is no injury or breathing problem. Keep the airway clear, check breathing, and do not give food or drink until they are fully alert. If you feel faint, lie down promptly rather than trying to walk. Do not drive until a clinician has discussed the episode, especially if it was unexplained or happened during activity.

Call emergency services if the person is not breathing normally, does not wake promptly, has a serious injury, chest pain, severe breathlessness, a new irregular heartbeat, seizure-like movements, or new weakness or trouble speaking. Emergency assessment is also needed when fainting occurs during exercise or with a very high blood pressure reading and neurological symptoms. These can be warning signs of Stroke or a heart problem.

Describe what happened before, during, and after the episode, including food, fluids, heat, exertion, warning symptoms, and injuries. Ask whether you need an ECG, medicine review, or a structured blood pressure check, and how to respond if dizziness returns.