Call your local emergency number if someone who has lost consciousness is not waking quickly, is not breathing normally, has chest pain, an irregular or racing heartbeat, trouble speaking or moving, a seizure, or a serious injury. Fainting during exercise or while lying down also needs emergency care. Even if the person wakes up and feels better, arrange prompt medical assessment after any unexplained blackout, especially a first episode.
When Is a Sudden Loss of Consciousness a Medical Emergency?
Sudden loss of consciousness means a person briefly or persistently becomes unresponsive and cannot respond normally to people around them. A brief faint, also called syncope, may occur for reasons such as a temporary drop in blood pressure. However, loss of consciousness can also be associated with serious heart problems, injury, low blood sugar, or other urgent medical conditions. According to MedlinePlus, unconsciousness or a sudden unexplained change in mental awareness should be treated as a medical emergency.
Call emergency services immediately if a person loses consciousness and experiences any of the following warning signs:
- They cannot be woken within about one minute, remain unresponsive, or do not return to their usual level of awareness.
- They are not breathing normally, are gasping, or have difficulty breathing.
- They have chest pain, chest pressure, or a racing, pounding, or irregular heartbeat.
- They develop difficulty speaking, sudden vision changes, weakness, or difficulty moving an arm or leg.
- They have a seizure, prolonged shaking, or significant confusion after the episode.
- They sustain a serious injury, particularly a head, neck, or back injury, during the fall.
- They faint during physical exercise or while lying down.
These warning signs are important even when the person regains consciousness. The UK National Health Service (NHS) specifically advises emergency help when fainting is accompanied by incomplete recovery, breathing problems, chest pain, palpitations, significant injury, seizure-like activity, or an episode during exercise or while lying down. Do not wait for symptoms to become worse before seeking help.
What Should You Do When Someone Suddenly Passes Out?
Act promptly if someone collapses and does not respond. Make sure the surrounding area is safe, check whether the person responds to your voice or gentle touch, and ask someone nearby to contact emergency services. Check for normal breathing while help is on the way. Do not assume that the person is simply asleep or that they will recover without assistance.
According to Mayo Clinic's first-aid guidance for fainting, a person who has fainted should not be brought upright too quickly, and emergency help is needed if they do not regain consciousness within about a minute. The appropriate first-aid steps depend on whether the person is responsive, breathing normally, and possibly injured.
First-aid steps while waiting for help
- If the person is not breathing normally: Call emergency services and begin cardiopulmonary resuscitation (CPR) if you can. Follow the emergency dispatcher's instructions and use an automated external defibrillator (AED) if one is available.
- If the person is breathing but remains unresponsive: Keep their airway clear. If you do not suspect a neck or spinal injury, place them in the recovery position when appropriate. If an injury is possible, avoid unnecessary movement and follow the emergency dispatcher's instructions.
- If the person has fainted and is now responsive: Help them remain lying flat in a safe place. If there is no suspected injury and they can tolerate it, raising their legs may help. Do not let them stand up suddenly.
- While waiting: Stay with the person, monitor their breathing and responsiveness, and keep them comfortable. Do not give food, drink, or oral medication to someone who is unconscious or not fully alert. Do not slap them or splash water on their face to try to revive them.
Should You Seek Medical Care After Waking Up From a Faint?
Yes. Anyone who has experienced an unexplained loss of consciousness should arrange medical evaluation, even if they feel completely normal afterward. A short episode does not establish that the cause was harmless, and symptoms may settle before the underlying reason is understood. The NHS recommends seeing a healthcare professional after fainting to help determine what caused it. A first episode, repeated episodes, or fainting accompanied by new symptoms deserves particular attention.
How quickly you need care depends on what happened and how completely you recovered. If emergency warning signs occurred, call emergency services rather than arranging a routine appointment. If the person recovered fully and has no emergency warning signs, contact a healthcare professional promptly for advice about the next steps. Repeated blackouts should not be ignored, even when each episode appears brief.
Which Circumstances Make a Blackout More Concerning?
The circumstances surrounding an episode can help determine how urgently it needs to be assessed. The American Heart Association notes that fainting during exertion, fainting associated with palpitations, and a family history of heart disease at a young age or sudden death may raise concern for a heart-related cause.
Pay particular attention if loss of consciousness occurs without an obvious warning, happens repeatedly, or is accompanied by unexplained breathlessness. A known heart condition or a family history of an inherited heart problem can also affect the assessment. These circumstances do not establish a diagnosis, but they are important reasons to seek timely medical evaluation. If an episode occurs during exercise or while lying down, seek emergency care even if consciousness returns quickly.
Does Age Affect How Quickly Someone Needs Help?
Yes. The appropriate assessment can depend on the person's age, medical history, and the circumstances of the episode. Fainting can occur in children, teenagers, and young adults, but an episode should not automatically be assumed to be harmless. Loss of consciousness during exercise, repeated episodes, or symptoms such as chest pain, breathing difficulty, or an abnormal heartbeat require urgent attention at any age.
Older adults may have a greater risk of complications related to fainting, including injuries from a fall. In particular, an older adult who loses consciousness without warning should receive timely medical assessment. People with known heart disease, diabetes, or other important medical conditions should also tell the healthcare professional about these conditions when seeking care.
What Will a Healthcare Professional Check After a Blackout?
An assessment generally begins with questions about what happened before, during, and after the episode. The clinician may ask whether the person was standing, sitting, lying down, or exercising; whether they felt dizzy or had changes in vision beforehand; approximately how long they were unresponsive; and how quickly they recovered. Information from someone who witnessed the event can be especially useful if the person cannot remember what happened.
The healthcare professional will also consider medical conditions, current medicines, previous episodes, and relevant family history. The examination may include checking heart rate, blood pressure, and the nervous system, along with an electrocardiogram (ECG) to assess the heart's electrical activity. Other tests may be recommended according to the findings. Sharing an accurate account of the episode can help the clinician decide whether further urgent assessment is needed.
How Can You Prepare if Another Episode Occurs?
Do not delay emergency treatment to gather information. Once the person is safe and receiving appropriate care, it may help to record what they were doing immediately before the episode, any symptoms they reported, how long they were unresponsive, whether there were movements or injuries, and how they behaved after waking. A witness can provide details that the affected person may not remember.
Keep a current list of medicines and relevant medical conditions available for the healthcare team. Until the cause has been assessed, avoid driving or other activities in which another episode could put the person or others at risk. Ask the treating professional when it is safe to resume these activities.