Headache: Red Flags & Emergency Signs
Most headaches are benign, but sudden severe onset, progressive worsening, or association with neurological signs can indicate subarachnoid haemorrhage, meningitis, or hypertensive emergency.
If you have this symptom right now
Call 999 (UK) / 112 (EU) / 911 (US) immediately if any emergency warning signs are present. Do not drive yourself. Do not wait to see if it improves.
🚨 Call 999 / 112 Immediately
- ⚠Thunderclap headache — reaches maximum severity within 60 seconds (subarachnoid haemorrhage until proven otherwise)
- ⚠Worst headache of life, especially if sudden onset
- ⚠Headache with fever, neck stiffness, and photophobia — meningitis
- ⚠Headache with focal neurological signs (arm weakness, slurred speech, visual loss) — stroke
- ⚠Headache with loss of consciousness or altered mental state
- ⚠Headache in immunocompromised patient (HIV, chemotherapy) — fungal meningitis, cerebral toxoplasmosis
⚡ See a Doctor Today
- •New severe headache in a patient over 50 (new-onset headache = temporal arteritis until excluded)
- •Headache waking from sleep or worse on lying flat (raised intracranial pressure)
- •Progressive headache over days to weeks with vomiting
- •Headache following head trauma (even minor) — subdural haematoma
- •Headache with jaw claudication or scalp tenderness in elderly — temporal arteritis
High-Risk Combinations
When headache occurs together with any of these symptoms, urgency increases significantly:
Meningitis, encephalitis, or brain abscess — emergency assessment
Nuchal rigidity = meningism until proven otherwise
Raised ICP pattern: headache + projectile vomiting
Hypertensive emergency, raised ICP, or stroke
Photophobia with headache = meningeal irritation
Conditions to Rule Out Urgently
CT head + LP if CT negative; 50% have sentinel headache
IV antibiotics within 1 hour of suspicion; do not wait for LP
MRI + CSF; IV aciclovir empirically for HSV encephalitis
CT/MRI brain; thrombolysis window 4.5 hours for ischaemic stroke
ESR + CRP; high-dose steroids to prevent blindness
BP >180/120 with organ damage; IV labetalol or nitroprusside
Condition Authority Pages
When to Call Emergency Services
- →Thunderclap headache or 'worst headache of life'
- →Headache + fever + neck stiffness (any two of three)
- →Headache with sudden loss of speech, vision, or limb movement
- →Headache following head injury with drowsiness or repeated vomiting