Is fainting dangerous? Causes and next steps

Fainting is when a person loses consciousness for a short time and then comes round. According to the NHS (the UK health service), it is usually not serious, but you should see a doctor to find the cause. The cause may be harmless, or it may be related to the heart: only testing shows which. So even if you have fainted only once, do not ignore it. Do not panic, but do not put off seeing a doctor.

According to the ACC summary of the 2018 ESC syncope guideline, at any age the most common cause is reflex fainting (this is what doctors call it). Heart-related causes come second. This means a heart cause is also possible, but it is not the first. The doctor determines through testing which one applies to you.

If you felt your heartbeat or felt dizzy before fainting or along with it, be sure to tell the doctor. According to AFib Matters, the website of the ESC and EHRA, if feeling your heartbeat comes with dizziness, you should see a doctor. If it comes with shortness of breath, fainting or chest pain, urgent medical help is needed.

According to the NHS, if a person who has fainted is not breathing or cannot be woken within 1 minute, you should call the emergency number. If the person is not breathing, call 103, start chest compressions (pressing on the chest to massage the heart indirectly) following the dispatcher's instructions and, if there is a defibrillator nearby, use it (according to the 2022 ESC guideline, resuscitation and defibrillator use by bystanders should become more common). If the person is breathing but does not wake up within 1 minute, call 103 and stay with them: in this case chest compressions are not needed. According to the NHS Wales website, fainting during physical exertion or while lying down needs urgent medical attention. According to the NHS and NHS Wales, chest pain, severe shortness of breath, a head injury, significant bleeding or confusion after fainting is also an emergency. This is not a complete list: if you feel unwell or are in doubt, do not hesitate to call 103.

The list of tests is not the same for everyone: the doctor sets it based on your situation. According to the ACC summary of the ESC guideline, long-term ECG monitoring of the heart rhythm is recommended if fainting keeps recurring, is severe, has an unknown cause, comes with features suggesting an arrhythmia (a heart rhythm disorder), and is likely to happen again. This monitoring may be done with an external or an implantable device.

If fainting is rare and its cause is not found even after full testing, an implantable loop recorder — a small monitor placed under the skin — may be recommended. In situations related to feeling your heartbeat, as AFib Matters stresses, the most important thing is an ECG recorded during symptoms. Not every person needs all of these tests.

Not everyone who has fainted needs a pacemaker. According to the 2021 ESC/EHRA guideline on cardiac pacing, dual-chamber pacing may reduce severe recurrent fainting, but in selected patients: people over 40 years of age in whom long pauses have been recorded on a rhythm recording. This concerns one situation; for other causes the decision is different, and it is made by a specialist.

• Write down what happened: where you were and what you were doing, how you felt before and after fainting, and how long it lasted. You cannot see yourself while you are unconscious, so ask the person who was with you what they saw.
• AFib Matters recommends a symptom diary for feeling your heartbeat: duration, triggers and accompanying symptoms. Notes about fainting are also helpful for the doctor.
• If young relatives in your family have had sudden death or heart disease, tell the doctor. According to the ACC summary of the 2022 ESC guideline, if there has been an early and unexpected sudden death in the family, an ECG and echocardiography are recommended for first-degree relatives (parents, brothers and sisters, children). The doctor decides who needs them.
• Ask your doctor about driving. This article does not give information about driving rules.