Headache is one of the most common reasons people present to GP surgeries and one of the most common reasons they Google symptoms at 2am, convinced they have a brain tumour.
Let me say this upfront: the vast majority of headaches — well over 90% — are primary headaches (tension headaches or migraines) or are related to obvious causes (dehydration, alcohol, sleep deprivation, stress). They are not dangerous.
But a small proportion of headaches are caused by something serious. The challenge is distinguishing them. Neurologists have a set of "red flag" features that, when present, mean a headache needs urgent investigation. I am going to share those with you.
The headache red flags — memorise these
These are the features that warrant same-day or emergency assessment:
1. Thunderclap headache: Severe headache reaching maximum intensity within seconds to a minute. "The worst headache of my life." This is the classic presentation of a subarachnoid haemorrhage (bleeding around the brain) until proven otherwise. Call 999.
2. Fever + headache + stiff neck: The triad of bacterial meningitis. Other features: sensitivity to light, rash that doesn't fade when pressed (glass test). Call 999.
3. Neurological symptoms: Headache with sudden vision loss, double vision, speech difficulty, facial weakness, arm or leg weakness, confusion. Call 999 — possible stroke.
4. Headache after head injury: Especially if there was loss of consciousness, amnesia, vomiting, or the headache is worsening. Go to A&E.
5. Headache in someone with cancer: A new or changed headache in someone with known cancer (especially cancers that spread to the brain) needs same-day assessment.
6. Headache on waking, worse on bending forward, or with coughing/straining: Can indicate raised intracranial pressure. Needs assessment.
7. New headache in someone over 50: New-onset headache in an older adult warrants more investigation than in a younger person. Temporal arteritis (giant cell arteritis) causes headache in people over 50 — it can cause blindness if untreated.
8. Worsening headache over weeks: A headache that progressively worsens over weeks is more concerning than one that has been stable for years.
Common headache types — the non-dangerous ones
Tension-type headache
The most common headache type. Features:
- Pressure or tightening — described as a band around the head or a weight on top
- Both sides of the head
- Mild to moderate severity
- Not worsened by physical activity
- No nausea, no light sensitivity (or mild)
Causes: stress, poor posture, prolonged screen use, muscle tension in neck and shoulders, dehydration, sleep deprivation.
Treatment: paracetamol or ibuprofen, hydration, rest, addressing the underlying trigger. Regular tension headaches may benefit from amitriptyline (a low-dose prescription medication used preventively).
Migraine
A distinct neurological condition. Features:
- Moderate to severe, often one-sided pulsing or throbbing pain
- Worsened by physical activity (climbing stairs, walking)
- Associated with nausea and/or vomiting
- Sensitivity to light (photophobia) and sound (phonophobia)
- Lasts 4–72 hours untreated
- May be preceded by aura (visual disturbance — zigzag lines, blind spots, or flashing lights — lasting 20–60 minutes)
Migraine is significantly underdiagnosed. Many people have had migraines for years and were told they were "bad headaches."
Treatment: Simple analgesia (ibuprofen + paracetamol together) taken early. Triptans (sumatriptan) for established migraine — very effective, available from pharmacies without prescription in the UK for diagnosed migrainers. Anti-emetics (metoclopramide) for nausea. Rest in a dark, quiet room.
Prevention: If migraines are frequent (more than 4 per month), preventive medication (propranolol, topiramate, amitriptyline, or newer CGRP inhibitors) should be discussed with your GP or neurologist.
Case study: Two headaches, two very different outcomes
Amara, 32: Woke at 6am with a headache she described as "like a band across my forehead." It was a 5/10 in severity. She had been stressed at work and had slept badly. She had similar headaches before, though not recently. She took paracetamol, drank a large glass of water, and went back to sleep. The headache resolved over 3 hours.
David, 45: Was watching television when he developed a sudden, severe headache — "like something exploded in my head." Severity 10/10. Maximum intensity within 30 seconds. He called 999. CT scan in A&E showed a subarachnoid haemorrhage from a cerebral aneurysm. He had emergency neurosurgery and survived with no neurological deficit.
The descriptor "like something exploding" or "the worst headache of my life" coming on suddenly should always be treated as an emergency.
Sources: NICE Clinical Guideline CG150 — Headaches in over 12s (2012, updated 2021); British Association for the Study of Headache (BASH) Guidelines; NICE NG128 — Suspected Neurological Conditions.