Quick answer: under NICE guideline NG232, an adult with a head injury needs a CT head within 1 hour if they have any high-risk feature: GCS 12 or less on initial assessment, GCS below 15 at 2 hours after the injury, a suspected open, depressed or basal skull fracture, a post-traumatic seizure, a focal neurological deficit, or more than one episode of vomiting. Adults who have had loss of consciousness or amnesia and have a further risk factor, such as age 65 or over, need a CT within 8 hours of the injury. Children have separate criteria, with a 4-hour observation option.
Head injury is one of the most common emergency department presentations and a reliable source of MRCEM questions. Most of them test whether you know who needs a scan, how quickly, and what changed in the 2023 update. This guide covers the criteria for adults and children as set out in NICE guideline NG232 (May 2023).
CT head within 1 hour: adults (16 and over)
Do a CT head within 1 hour of the risk factor being identified if the patient has any of the following:
- GCS of 12 or less on initial assessment in the emergency department.
- GCS of less than 15 at 2 hours after the injury.
- Suspected open or depressed skull fracture.
- Any sign of basal skull fracture: haemotympanum, panda eyes, cerebrospinal fluid leaking from the ear or nose, or Battle’s sign.
- Post-traumatic seizure.
- Focal neurological deficit.
- More than one episode of vomiting.
A provisional written radiology report should be available within 1 hour of the scan.
CT head within 8 hours: adults
If the patient has had loss of consciousness or amnesia since the injury, do a CT head within 8 hours of the injury if they also have any of these risk factors:
- Age 65 or over.
- Any current bleeding or clotting disorder.
- A dangerous mechanism of injury: a pedestrian or cyclist struck by a motor vehicle, an occupant ejected from a motor vehicle, or a fall from a height of more than 1 metre or 5 stairs.
- More than 30 minutes of retrograde amnesia for events immediately before the injury.
If the patient presents more than 8 hours after the injury, the scan should be done within 1 hour.
Anticoagulants and antiplatelets: what changed in 2023
This is the change most likely to be tested. For a patient with a head injury and no other indication for a scan who is taking an anticoagulant or an antiplatelet (other than aspirin alone), NICE now says to consider a CT head within 8 hours of the injury. The previous guideline said to scan all patients on anticoagulants.
- The recommendation covers warfarin, direct oral anticoagulants, heparins and antiplatelets such as clopidogrel.
- Aspirin on its own is excluded.
- A scan is more appropriate if a risk assessment is difficult, or if the patient might not return if they deteriorate.
CT head within 1 hour: children (under 16)
Do a CT head within 1 hour if the child has any of the following:
- Suspicion of non-accidental injury.
- Post-traumatic seizure with no history of epilepsy.
- GCS of less than 14 on initial assessment, or less than 15 in a baby under 1 year.
- GCS of less than 15 at 2 hours after the injury.
- Suspected open or depressed skull fracture, or a tense fontanelle.
- Any sign of basal skull fracture.
- Focal neurological deficit.
- In a baby under 1 year: a bruise, swelling or laceration of more than 5 cm on the head.
Children: one risk factor or more than one?
For children with none of the features above, count how many of these risk factors are present:
- Witnessed loss of consciousness lasting more than 5 minutes.
- Abnormal drowsiness.
- Three or more discrete episodes of vomiting.
- A dangerous mechanism of injury: a high-speed road traffic collision as a pedestrian, cyclist or vehicle occupant, a fall from a height of more than 3 metres, or a high-speed injury from a projectile or other object.
- Amnesia, antegrade or retrograde, lasting more than 5 minutes.
- Any current bleeding or clotting disorder (added in 2023).
| Number of risk factors | Action |
|---|---|
| More than one | CT head within 1 hour |
| Only one | Observe for at least 4 hours after the injury |
| One, then GCS below 15, further vomiting or further abnormal drowsiness during observation | CT head within 1 hour |
The observation option exists to limit radiation exposure in children, which is why the thresholds are higher than in adults.
Tranexamic acid
The 2023 guideline added tranexamic acid for isolated head injury:
- Give it to patients with a GCS of 12 or less who are not thought to have active extracranial bleeding.
- Give it as soon as possible, within 2 hours of the injury.
- Adults: 2 g intravenous bolus. Under 16s: 15 to 30 mg/kg, up to a maximum of 2 g.
Patients with a head injury and suspected active extracranial bleeding get tranexamic acid under the major trauma guidance.
Do not forget the cervical spine
A head injury is also a potential neck injury. In adults, CT is the first-line imaging for the cervical spine, and the Canadian C-spine rule is used to decide who needs imaging. Scan the cervical spine at the same time as the head if the patient has a GCS of 12 or less, is intubated, or has other areas being scanned for major trauma.
Admission and discharge
Admit patients with new, clinically significant abnormalities on imaging, a GCS that has not returned to 15, or continuing worrying signs such as persistent vomiting or severe headache. Involve an anaesthetist early for patients with a GCS of 8 or less, and discuss abnormal scans with a neurosurgeon.
Patients can go home when their GCS is 15, there are no other reasons to admit, and a responsible adult can supervise them. Give verbal and written head injury advice. NICE also highlights that a head injury of any severity can cause pituitary dysfunction, which may appear weeks or months later.
Common exam traps
- Vomiting thresholds: more than one episode in adults, three or more in children.
- GCS thresholds: 12 or less on arrival in adults, less than 14 in children, less than 15 in babies under 1 year.
- Age alone: being 65 or over only counts if there has also been loss of consciousness or amnesia.
- Scanning every anticoagulated patient: the 2023 guidance says consider a scan, and it excludes aspirin alone.
- Dangerous mechanism: a fall of more than 1 metre or 5 stairs in adults, more than 3 metres in children.
- Timing: the 8 hours runs from the injury, and the 1 hour runs from when the risk factor is identified.
Summary
- Adults need a CT within 1 hour for GCS 12 or less, GCS below 15 at 2 hours, skull fracture signs, seizure, focal deficit or more than one vomit.
- Adults with loss of consciousness or amnesia plus age 65 or over, a bleeding disorder, a dangerous mechanism or more than 30 minutes of retrograde amnesia need a CT within 8 hours.
- Consider a CT within 8 hours for patients on anticoagulants or antiplatelets other than aspirin alone.
- Children with more than one secondary risk factor need a CT within 1 hour. With only one, observe for at least 4 hours.
- Give tranexamic acid within 2 hours if the GCS is 12 or less.
Frequently asked questions
Who needs a CT head within 1 hour after a head injury?
Adults with a GCS of 12 or less on arrival, a GCS below 15 at 2 hours, a suspected open, depressed or basal skull fracture, a post-traumatic seizure, a focal neurological deficit or more than one episode of vomiting.
Do all patients on anticoagulants need a CT head?
No. Since 2023, NICE says to consider a CT within 8 hours for patients on anticoagulants or antiplatelets (excluding aspirin alone) who have no other indication for a scan.
How many vomits before a child needs a CT head?
Three or more discrete episodes count as a risk factor. A child with this as the only risk factor is observed for at least 4 hours, and scanned if there is further vomiting.
When is tranexamic acid given in head injury?
Within 2 hours of the injury in patients with a GCS of 12 or less: 2 g intravenously in adults, and 15 to 30 mg/kg (maximum 2 g) in children.
Next steps
Test yourself with our 20 free MRCEM SBA sample questions. For more, explore our Trauma resources and the head injury lessons in the Trauma course and the Paediatric Emergency Medicine course, or see the full question bank and mock tests in our membership plans.
Clinical content checked against NICE guideline NG232, Head injury: assessment and early management (May 2023), on 3 October 2026. This article is for exam preparation. In clinical practice, always follow the full guideline and your local protocol.