Heat syncope prevention: how to reduce fainting risk

Heat widens blood vessels near the skin so the body can release warmth. Sweating also removes fluid. If you stand still for a long time, less blood may return to the heart and brain, causing light-headedness or a brief loss of consciousness. Dehydration makes this response more likely. Early clues include weakness, nausea, blurred vision, dizziness and a feeling of warmth.

Drink water at regular intervals before and during heat exposure, unless a clinician has restricted your fluids. Choose loose, light clothing and take breaks in shade or air conditioning. Move your legs, flex your calves and avoid locking your knees when standing. Sit or lie down as soon as dizziness begins, preferably with your legs raised. Avoid sudden changes from lying or sitting to standing. If fainting has happened more than once, discuss possible contributors such as Anaemia, Atrial Fibrillation, Dehydration or Hypoglycaemia with a clinician.

Get urgent help if someone does not wake promptly, has trouble breathing, chest pain, a severe headache, seizure-like movements, serious injury or confusion. Seek medical assessment after a first faint, repeated episodes, fainting during exercise, or an episode without a clear heat trigger. Do not let a fainted person stand immediately; keep them lying down and monitor breathing.

Ask: Could my medicines or fluid restrictions affect fainting? Should I have my blood pressure checked lying and standing? Do my symptoms suggest a heart rhythm or blood sugar problem? What should I do before working or exercising in heat?