COVID and fainting: what should you know?

COVID-19 can be accompanied by fainting, but a blackout also has other possible causes and should be assessed carefully. Fever, reduced fluid intake, vomiting, diarrhoea, or standing up after resting can lower blood pressure and make someone pass out. Fainting may also occur independently of the infection, so do not assume COVID-19 explains it.

During an infection, dehydration and fever can reduce the circulating fluid available to the brain for a moment. Coughing, pain, anxiety, or prolonged standing may also trigger a brief reflex drop in blood pressure. Other problems, including anaemia, low blood sugar, or an irregular heart rhythm, can cause similar episodes. The details matter: whether there was warning dizziness, how long consciousness was lost, and whether there was chest discomfort or a racing heartbeat.

Lay the person flat and raise their legs if there is no injury or breathing difficulty. Loosen tight clothing, keep them cool, and do not give food or drink until they are fully alert. Once awake, small sips of fluid may help if swallowing is normal. Record the timing, fever, recent intake, medicines, and what the person was doing before the blackout. Arrange medical advice, particularly after a first episode or if the person is pregnant, older, or has heart disease.

Call emergency services for difficulty breathing, persistent confusion, severe weakness, a seizure, a serious injury, blue lips, or chest pain. Urgent assessment is also needed when fainting happens during exercise, without warning, while sitting or lying down, or with a fast or irregular heartbeat. Seek prompt medical advice if the person cannot keep fluids down, is passing very little urine, or has repeated episodes. These signs can point to dehydration, heart rhythm problems, or another condition needing treatment.

Ask whether the episode could be related to dehydration, blood pressure, blood sugar, anaemia, or heart rhythm. Discuss whether you need an examination, an ECG, or blood tests, and ask which medicines should be continued during the illness. It may help to ask how much fluid is suitable for you and what symptoms should trigger a return visit.