If someone is unconscious, first make sure the scene is safe for you, the person and anyone else nearby. Try to establish responsiveness by speaking loudly to the person and gently shaking their shoulders. If they do not respond, shout for help and call 999 immediately, preferably using speakerphone so the emergency call handler can guide you.
The next critical assessment is breathing: look for normal chest movement, listen and feel for normal breathing, and follow the call handler's instructions if you are uncertain. An unresponsive person with abnormal breathing, including gasping or irregular agonal breaths, should be treated as being in cardiac arrest and CPR should be started immediately. Current Resuscitation Council UK guidance emphasises that early recognition, an immediate 999 call, prompt CPR and early access to an AED are the key actions when cardiac arrest is suspected.
If an unconscious person is breathing normally, cardiac arrest is less likely, but unconsciousness remains a medical emergency until its cause is understood. If there is no indication of major trauma and the person is breathing normally, place them in the recovery position to help maintain an open airway and reduce the risk of choking on vomit or other material. Continue monitoring their breathing and responsiveness while waiting for emergency help.
Do not assume that because someone is breathing they are necessarily safe: unconsciousness can result from poisoning, low blood glucose, stroke, head injury, seizures, severe infection, alcohol or drug toxicity, or other serious conditions. The NHS specifically advises placing an unconscious person who is still breathing in the recovery position and continuing to check their breathing.
If the person is not breathing normally, begin CPR without delay. Normal breathing should not be confused with occasional gasps, snorting, irregular breaths or agonal breathing, which can occur during cardiac arrest and do not provide adequate circulation. The current adult basic life-support guidance recommends calling 999 as soon as possible for an unresponsive person and starting chest compressions when the person is unresponsive with abnormal breathing. If another person is present, one person should call the ambulance service and retrieve an AED while the other begins CPR. If alone, use the phone's speaker function so the emergency call handler can assist while you start treatment.
If there is a suspected spinal or major traumatic injury, unnecessary movement should generally be avoided unless movement is required to provide life-saving treatment or the environment is dangerous. Airway management takes priority over concerns about maintaining a perfectly still spine when someone cannot breathe adequately. If the person has fallen, been struck, drowned, suffered a serious head injury or been involved in a road collision, tell the ambulance service because the mechanism of injury affects subsequent care. A person who was briefly unconscious after a head injury but has not fully recovered, has repeated vomiting, seizures, weakness, speech problems or difficulty staying awake requires urgent medical assessment.
Do not give an unconscious person food, drink or oral medicines because they cannot safely protect their airway and may aspirate material into the lungs. Do not leave them alone to “sleep it off”, particularly when alcohol, drugs, poisoning, head injury or unexplained illness may be involved. If poisoning is suspected, call 999 for serious symptoms or loss of consciousness, avoid inducing vomiting, and preserve containers or packaging that could help clinicians identify the substance. An unconscious person who is breathing normally should remain under continuous observation because their condition can deteriorate into respiratory or cardiac arrest.
If the person is unconscious because of severe low blood glucose, the response differs from ordinary fainting or simple sleep. A person with severe hypoglycaemia who has become unconscious must not be given food or drink because they cannot swallow safely. The NHS advises placing such a person in the recovery position and, where an appropriate glucagon injection is available and someone knows how to use it, administering glucagon. This illustrates why identifying the cause can be useful, but the first priorities remain responsiveness, airway, breathing and rapid access to emergency care.
A brief faint is different from prolonged unconsciousness. Fainting, or syncope, usually results from a temporary reduction in blood flow to the brain and often resolves rapidly, but a person who cannot be woken within a minute, does not fully recover, has difficulty speaking or moving, has chest pain or abnormal palpitations, has a seizure, has seriously injured themselves, faints during exercise or faints while lying down needs emergency assessment. Even when a person wakes quickly, an unexplained first episode of fainting should be medically assessed. The distinction matters because a transient faint can be benign whereas persistent unconsciousness may represent cardiac arrest, stroke, poisoning, seizure, severe metabolic disturbance or another life-threatening condition.
The fundamental principle is to prioritise immediate threats to life rather than trying to diagnose the person before acting. Check safety, responsiveness and breathing, call 999 early, begin CPR if the person is unresponsive and not breathing normally, use an AED as soon as it becomes available, or place a normally breathing unconscious person in the recovery position while monitoring them.
CPR has a low risk of causing serious harm when performed for presumed cardiac arrest, and current UK guidance specifically encourages lay rescuers to act rather than delay because of fear of doing something wrong. The emergency call handler can provide real-time instructions, making it appropriate to act even when the rescuer has limited first-aid experience.
