What should you know about blood sugar fainting?

Very low glucose can impair brain function and cause sweating, shaking, confusion, unusual behaviour, or loss of consciousness. Fainting can also result from dehydration, a sudden blood-pressure drop, anaemia, or an abnormal heart rhythm. A person who faints should not be diagnosed from the event alone.

Tell a clinician what happened before, during, and after the blackout. Useful details include standing or exertion, skipped meals, heat, illness, medicines, warning symptoms, injury, and how quickly awareness returned. A glucose reading taken during symptoms can help, but a later normal reading does not explain away the event.

Heart-related fainting may happen with little warning, especially during exertion or with palpitations. A review may include blood pressure, glucose, blood count, an examination, and heart-rhythm testing.

Lay the person flat and raise their legs if there is no suspected injury. Check breathing, loosen tight clothing, protect them from heat, and do not give food, drink, or tablets until they are fully awake and able to swallow. If they have diabetes, follow the agreed emergency plan once safe to do so.

After recovery, they should avoid driving, heights, swimming alone, and operating machinery until medically assessed. Arrange a prompt appointment even if they feel normal afterwards.

Call emergency services if the person is not breathing normally, does not wake promptly, has chest pain, severe breathlessness, a seizure, serious injury, new weakness, speech trouble, persistent confusion, or faints during exercise. Urgent assessment is also needed for repeated episodes or fainting with palpitations.

Ask whether low glucose, dehydration, anaemia, or a heart-rhythm problem could explain the event; whether medicines need adjustment; and which symptoms require emergency action. Ask when it is safe to drive and whether a glucose meter or other monitoring is useful.