Loss of consciousness after a head injury

Emergency numbers
United States: 911
United Kingdom: 999 or 112
European Union: 112
Elsewhere: your local emergency number

Short answer. Loss of consciousness after a blow to the head is important information, even if it lasts only a few moments. Its presence alone does not establish the severity of the injury, and its absence does not rule out concussion. Healthcare professionals need the whole picture: the person’s condition on waking, memory, changing symptoms, the mechanism of injury and risk factors.

Important. If the person is unconscious, does not wake normally or becomes difficult to wake after a head injury, call emergency services immediately. A seizure, weakness on one side or a new speech problem also requires emergency help. If they lost consciousness and then woke up, medical assessment in an emergency department is still necessary.

Why does waking quickly not establish that everything is fine?

It is easy to imagine that a serious injury means prolonged unconsciousness, while someone who opens their eyes quickly has nothing seriously wrong. This assumption is misleading. Assessment after a head injury takes account of changes in alertness, the neurological examination and other signs, not just the length of the episode.

The UK’s NICE guidelines recommend referral to an emergency department for any loss of consciousness related to a head injury, even if the person has regained consciousness. There, a professional decides which observations and examinations are appropriate; CT scanning is not automatic in every situation, and the indications depend on several criteria.

For example, after a fall, someone lies motionless for a few seconds, sits up, says they are fine and then repeatedly asks where they are. Waking up is a favourable sign, but both the period of unconsciousness and the confusion afterwards must be reported to healthcare staff.

What should you do if the person does not wake normally?

Contact emergency services immediately and explain that there has been a head injury with loss of consciousness. Follow their instructions: they can guide you according to the person’s breathing and any suspected neck injury. Do not improvise moving them or performing manoeuvres that might worsen an injury, and do not leave them alone.

Do not try to make them walk to check that everything is fine. Also avoid giving them food or drink if their alertness is impaired. If they have a seizure, breathe abnormally, develop new weakness or cannot stay awake, report this at the start of the call.

Someone who wakes up but whose alertness then deteriorates also needs emergency help. A complication may become apparent during observation; initial improvement must therefore not prevent you from acting on a concerning change.

How can you describe the episode if you did not see exactly what happened?

The duration of unconsciousness is sometimes an estimate. It is fine to say you do not know. An honest account in chronological order is more useful than an uncertain number. To prepare for the medical discussion, keep four points in mind:

1. Before the impact: a fall, accident, exertion or feeling faint beforehand; did the person seem to lose consciousness before falling?

2. During the episode: witnesses present, lack of response, any abnormal movements and approximate duration.

3. On waking: whether speech was understandable, confusion, repeated questions, memory of the event and ability to recognise those close to them.

4. Since then: headache, vomiting, drowsiness, new symptoms and how they have changed; medication such as anticoagulants.

This sequence also helps distinguish loss of consciousness caused by the impact from a possible fainting episode before the fall. These are different medical questions, even though both can lead to a head injury.

Can you have a concussion without losing consciousness?

Yes. Concussion can cause confusion, difficulty thinking clearly, headache, dizziness or memory problems without fainting. The CDC notes that symptoms can appear immediately or later. Not losing consciousness must therefore not be used as a negative test at home.

Conversely, loss of consciousness alone does not indicate the type of injury present or how long recovery will take. The examination looks in particular for other risk factors and, when indicated, acute injuries visible on imaging.

What happens after an emergency department assessment?

Depending on the findings, the person may need observation, tests or admission to hospital. If discharge home is authorised, the team should provide appropriate instructions, explain which signs require a return for care, and check that suitable supervision is possible. The UK’s NICE guidelines specify that a responsible adult should stay with the person during the first 24 hours after the injury, in line with the discharge instructions.

Families do not need to invent their own schedule of night-time waking or memory tests. They primarily need to know the signs of deterioration, whom to call and which activities to avoid temporarily. Guidance on returning to work, education, sport or driving depends on progress and medical advice.