← All articles
Clinical Resources
Acute Severe Headache: Migraine vs Red Flags
How to distinguish benign migraine from serious secondary headaches, including subarachnoid haemorrhage and meningitis, and when to call 999.
Why this matters
Headache is one of the most common presentations at a pharmacy counter, and the vast majority are benign. Tension-type headache, migraine, and cluster headache are primary conditions with recognised patterns that pharmacists can identify and manage. However, a small number of headaches are secondary to serious pathology, and missing them carries significant risk.
The most critical condition to recognise is subarachnoid haemorrhage, which presents as a thunderclap headache: sudden and severe, reaching maximum intensity within minutes, described as the worst headache of the patient's life. Raised intracranial pressure, meningitis, giant cell arteritis, and hypertensive crisis are further secondary causes. Community pharmacists are often the first point of contact and must know which features demand immediate action.
Red flags vs more likely benign
| Feature | More likely benign | Red flag ⚠ |
|---|---|---|
| Onset | Gradual, over minutes to hours | Thunderclap: reaches maximum intensity within 5 minutes; worst-ever headache |
| Severity | Mild to moderate (tension) or moderate to severe (migraine) | Worst headache of life; described as unprecedented by the patient |
| Pattern | Consistent with known personal headache history | New type of headache, or a substantial change from the usual headache character |
| Fever | No associated fever | Worsening headache with fever: possible meningitis or encephalitis |
| Neurology | None, or fully reversible migraine aura lasting 5 to 60 minutes | New neurological deficit, confusion, personality change, or impaired consciousness |
| Neck stiffness | None | Neck stiffness with headache and fever: meningitis until proven otherwise |
| Trigger | Stress, dietary, menstrual, or sleep-related triggers | Cough, Valsalva, exertion, or sneezing; or headache worsening on lying down |
| Age / other | Any age; no scalp tenderness or jaw pain | Age 50 or over with new temporal headache, jaw pain on chewing, or scalp tenderness |
What to do in pharmacy
Call 999 immediately for any thunderclap headache: a sudden, severe headache reaching maximum intensity within 5 minutes, especially if described as the worst headache of the patient's life. Also call 999 for headache accompanied by impaired consciousness, a new neurological deficit, seizure, or neck stiffness with fever. These presentations may indicate subarachnoid haemorrhage or meningococcal meningitis; both can deteriorate rapidly and require emergency hospital assessment. Do not supply analgesia and advise the patient to wait; call 999 and stay with them.
Refer to A&E or arrange same-day GP review for any new headache with red flag features that does not require 999. This includes new-onset headache with vomiting and no other obvious cause; new headache in an immunocompromised patient; headache triggered by cough, Valsalva, exertion, or sneezing; or any headache that has substantially changed in character from the usual pattern. In patients aged 50 or over, new unilateral temporal headache with jaw pain on chewing or scalp tenderness should be referred urgently as possible giant cell arteritis: untreated, this can cause sudden permanent sight loss.
Self-care is appropriate for an established, recognised migraine or tension-type headache that is consistent with the patient's previous pattern and has no red flag features. For tension-type headache: aspirin, ibuprofen, or paracetamol. For migraine: aspirin 900 mg, ibuprofen 400 mg, or paracetamol; sumatriptan 50 mg tablets (Imigran Recovery) are available over the counter for adults aged 18 to 65 with a confirmed diagnosis of migraine; prochlorperazine buccal (Buccastem) is available OTC for nausea. Safety-net: seek urgent help if the headache changes character, becomes the worst the patient has ever had, or is accompanied by fever, neck stiffness, visual change, or any neurological symptoms. Warn patients using acute headache treatment on more than 10 days per month about medication overuse headache.
Key takeaways
- A thunderclap headache (maximum intensity within 5 minutes, worst ever) is subarachnoid haemorrhage until proven otherwise: call 999 and do not supply analgesia.
- Any new headache with fever, neck stiffness, neurological deficit, or confusion requires emergency assessment; OTC analgesia is not appropriate.
- Sumatriptan 50 mg is available over the counter for adults with a confirmed migraine diagnosis; warn patients using acute treatment more than 10 days per month about medication overuse headache.
Download the checklist
Professional disclaimer: This article is for educational purposes
to support healthcare professionals' clinical decision-making. It does not replace
independent professional judgement, local pathways, NICE guidance, or standard
medical literature. Members of the public must not use this resource for
self-diagnosis and should seek prompt advice from a qualified healthcare
professional if experiencing chest pain, palpitations, fainting, or breathlessness.