What should you know about fainting from not eating?

Going without food may leave you weak, shaky, sweaty, irritable, dizzy or unable to concentrate. The risk is greater with vomiting, diarrhoea, heat, strenuous activity, alcohol or medicines that lower glucose. A person with diabetes may develop hypoglycaemia, which can progress to confusion or loss of consciousness. Not every faint after a missed meal is caused by glucose: dehydration, anaemia and heart rhythm problems such as Atrial Fibrillation can look similar.

A clinician will consider your eating pattern, fluid intake, medical history and medicines. Repeated episodes, fainting despite eating normally, or symptoms without an obvious trigger deserve assessment rather than repeated self-treatment.

At the first warning, sit or lie down somewhere safe. If you are fully awake and can swallow, take a suitable snack and water; follow your personal diabetes plan if you have one. Never give food or drink to someone who is unconscious or struggling to swallow. Once recovered, eat regular balanced meals and carry a snack when delays are likely, while avoiding driving if symptoms are recurring.

Call emergency services if someone is unconscious, confused, having a seizure, breathing abnormally, injured, or cannot safely swallow. Seek urgent assessment for chest pain, severe breathlessness, a very fast or irregular heartbeat, fainting during exercise or a blackout with no warning. Arrange a routine review for repeated faintness or unexplained weight loss.

Ask whether glucose testing, blood tests or a medication review is appropriate. Explain how long you had gone without food, what you drank, your warning symptoms and how quickly you recovered.