Causes of fainting in teenagers

Fainting, also called syncope, is a brief loss of consciousness caused by temporarily reduced blood flow to the brain. Feeling warm, nauseated, light-headed, or having tunnel vision beforehand can fit a reflex faint. Dehydration from sweating, vomiting, diarrhoea, or not drinking enough can reduce circulating fluid. Low blood sugar after missing food may cause shakiness, sweating, confusion, or collapse; read about Hypoglycaemia for more context.

Anaemia can reduce oxygen delivery and may occur with tiredness, breathlessness, paleness, or heavy menstrual bleeding. A racing or irregular heartbeat, fainting during exercise, chest discomfort, or a family history of sudden cardiac death raises concern for a heart cause. A clinician may ask what happened before and after the event and review medicines, food and fluid intake, illness, and menstrual history.

Lay the teenager flat and raise their legs if possible. Loosen tight clothing, keep the area cool, and check breathing. Do not give food or drink until they are fully alert. Once recovered, small sips of water and a snack may help when dehydration or a missed meal is plausible. Record the setting, warning symptoms, duration, injury, movements, and recovery, and arrange a medical review after a first unexplained episode.

Call emergency services if the teenager is not waking normally, has trouble breathing, chest pain, a sustained pounding heartbeat, a serious injury, seizure-like activity, or faints during exercise. Seek prompt assessment for repeated episodes, fainting without warning, or a family history of an inherited heart condition. Dehydration may need urgent treatment when the teenager cannot keep fluids down, is unusually drowsy, or passes very little urine.

Ask whether blood pressure should be checked lying and standing, whether blood tests could assess anaemia or glucose, and whether an electrocardiogram is appropriate. Mention any new medicine, supplements, restrictive eating, heavy periods, recent illness, and symptoms such as palpitations. Ask when sport, driving, or swimming can safely resume.