When Should You Actually Worry About a Headache? A Certified GP Explains

Written by Dr. Simon Khela MBChB MRCGP, GMC Registered Doctor

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Almost everyone gets headaches, and the overwhelming majority are entirely harmless: a tension headache after a stressful day, a migraine, or the dull throb of dehydration or too much screen time. That's precisely what makes the dangerous minority so easy to miss. In clinic, one of the most useful things I can do isn't reassure everyone that their headache is fine, or send everyone for a scan; it's help people tell the difference.

This article sets out, clearly and without unnecessary alarm, which headache symptoms genuinely warrant urgent attention, which are worth a routine GP conversation, and which are simply part of being human. Given how much this genuinely matters, I've deliberately put the emergency information first.

Quick Answer: Red Flags at a Glance

If you take nothing else from this article, take this.

• Call 999 or go to A&E immediately if your headache came on suddenly and reached its worst point within seconds to minutes (a “thunderclap” headache), or if it's accompanied by slurred speech, facial drooping, arm or leg weakness, a seizure, confusion, loss of consciousness, or a rash that doesn't fade under pressure.
• Seek urgent same-day medical assessment (GP, NHS 111, or walk-in) if you're over 50 with a new headache, especially with scalp tenderness or jaw pain when chewing; if your headache is worsening day by day; or if it's triggered or worsened by coughing, straining, or lying flat.
• Book a routine GP appointment if your headaches are becoming more frequent, are different from your usual pattern, or are affecting your daily life, even without any of the features above.
• Most headaches, even severe ones, are primary headaches, meaning tension-type headache, migraine, or cluster headache, and are not a sign of anything sinister.

The Reassuring Truth: Most Headaches Are Not Dangerous

The vast majority of headaches that bring people into my consulting room fall into one of three categories: tension-type headache (a dull, band-like pressure, usually on both sides), migraine (often one-sided, throbbing, with nausea or sensitivity to light and sound), or, less commonly, cluster headache (severe, one-sided pain around one eye, often with a watering eye or blocked nostril on the same side). We've covered migraine symptoms and triggers in more depth elsewhere, since it's a genuinely distinct condition worth understanding in its own right rather than just “a bad headache.”

None of these primary headache types, however unpleasant, indicate an underlying dangerous cause. The job of red flag screening isn't to make every headache frightening; it's to pick out the much smaller group of headaches that are secondary, meaning caused by something else, such as bleeding, infection, or raised pressure inside the skull.

A rough guide to telling the three common primary types apart:

• Tension-type headache: a dull, pressing or band-like tightness, usually on both sides of the head, without nausea or significant light sensitivity. It's the most common type by far.
• Migraine: often one-sided, throbbing or pulsating, moderate to severe, and typically accompanied by nausea, sensitivity to light or sound, or made worse by routine physical activity. Some people also experience an aura beforehand, such as flickering lights or visual blind spots.
• Cluster headache: intense, one-sided pain centred around or behind one eye, often with a watering or red eye, drooping eyelid, or blocked nostril on the same side. Attacks are typically short but severe, and tend to cluster in bouts over weeks, hence the name.

Red Flags That Need Emergency Care (Call 999 or Go to A&E)

These features mean you shouldn't wait, drive yourself, or try to “see how it goes”:

• A thunderclap headache: sudden, severe pain that reaches its peak within seconds to a few minutes, often described as the worst headache of your life. This is the classic warning sign of a bleed around the brain (subarachnoid haemorrhage) and needs same-day emergency assessment even if the pain has since eased.
• Headache with stroke symptoms: facial drooping, arm or leg weakness, slurred or garbled speech, or sudden vision loss. Treat this exactly as you would treat suspected stroke, because it may be one.
• Headache with fever, neck stiffness, a rash that doesn't fade when a glass is pressed against it, or extreme drowsiness or confusion: these are classic features of meningitis, a genuine medical emergency.
• Headache following a significant head injury, particularly with vomiting, drowsiness, or confusion.
• Headache with a new seizure, loss of consciousness, or a rapidly reduced level of alertness.

One group deserves particular caution after any head injury: people taking blood-thinning medication such as warfarin, apixaban, or rivaroxaban. Because these medications increase the risk of bleeding inside the skull, even a headache after a relatively minor bump to the head warrants a lower threshold for emergency assessment than it would in someone not taking these drugs.

Red Flags That Need Urgent Same-Day Assessment

These don't always need an ambulance, but they do need same-day medical attention, typically via an urgent Private GP appointment, NHS 111, or a walk-in service:

• A new headache in someone over 50, particularly with tenderness over the scalp or temples, jaw pain when chewing, or visual disturbance. This combination raises the possibility of giant cell arteritis, a treatable condition that can cause permanent vision loss within days if it's missed, which is why it's treated as a same-day priority rather than a routine referral.
• A headache that's steadily getting worse over days or weeks, rather than coming and going.
• A headache that's worse first thing in the morning, wakes you from sleep, or is triggered or made worse by coughing, sneezing, bending forward, or straining, which can suggest raised pressure inside the skull.
• A new type of headache in someone with a history of cancer, or in someone with a weakened immune system, for example due to HIV or immunosuppressive medication.
• A new or unusual headache during pregnancy, particularly with visual disturbance, swelling, or high blood pressure, which needs prompt assessment to rule out pre-eclampsia.

When to See Your GP (Not Urgent, But Worth Checking)

Plenty of headaches don't tick any of the boxes above but are still worth discussing with a GP rather than just managing indefinitely with painkillers:

• Headaches that are becoming more frequent or more severe over time, even gradually.
• A headache pattern that feels distinctly different from your usual migraines or tension headaches.
• Headaches that are starting to interfere with work, sleep, or daily activities.
• Taking painkillers for headaches on 10 or more days a month, which raises the possibility of medication overuse headache, covered in more detail below.

If your situation fits into this category rather than the two above, an online GP consultation is often a sensible first step to work out whether further assessment or simple treatment adjustments are what's needed.

Headache Red Flags at a Glance

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Giant Cell Arteritis: The Over-50s Red Flag Worth Knowing

This condition deserves its own mention because it's genuinely time-critical and not always well known outside medicine. Giant cell arteritis is inflammation of blood vessels, typically in people over 50, and classically causes a new headache with scalp tenderness (it can hurt to brush your hair), pain in the jaw when chewing, and sometimes visual disturbance. Left untreated, it can cause sudden, permanent blindness, which is why same-day treatment with high-dose steroids is started on clinical suspicion, often before test results are back. Diagnosis usually involves urgent private blood tests to check inflammatory markers, alongside a same-day specialist opinion.

Managing a Straightforward Headache at Home

For headaches without any of the features above, simple self-care is usually all that's needed:

• Stay hydrated and eat regularly; both dehydration and missed meals are common, easily fixed triggers.
• Simple analgesia such as paracetamol or ibuprofen, used occasionally and at the recommended dose, is reasonable for most tension-type headaches and migraines.
• Rest in a quiet, dark room can help significantly during a migraine attack.
• Keep a brief headache diary, noting frequency, triggers, and what helps, which is genuinely useful both for your own understanding and for any future GP conversation.
• Be mindful of how often you're reaching for painkillers; more than 10 to 15 days a month is the threshold where medication overuse headache becomes a realistic possibility, covered in more detail below.

Medication Overuse Headache: The Hidden Everyday Culprit

This is one of the most common causes of chronic daily headache that I see, and one of the least intuitive, because the instinctive response to a worsening headache is usually to take more painkillers, not fewer. Regularly using painkillers, including over-the-counter options, on 10 or more days a month can paradoxically cause more frequent headaches over time. The treatment, counterintuitively, is to stop the painkillers, usually under guidance, which often makes things temporarily worse before they improve.

Common Myths and Misconceptions

• “A severe headache always means something is seriously wrong.” Severity alone is a poor predictor; a migraine can be excruciating and still be entirely benign, while some dangerous causes start relatively mildly.
• “If it's not the worst headache of my life, it's not serious.” Red flags are about the specific pattern and accompanying symptoms, not simply how much something hurts.
• “Headaches are always caused by stress or dehydration.” These are common triggers for primary headaches, but assuming this explanation for every headache risks missing a genuinely different pattern.
• “Taking more painkillers is always the safe option.” As covered above, frequent painkiller use can itself become the cause of chronic headaches.
• “A brain scan will settle the question either way.” Scans are appropriate when there's a genuine clinical indication, not as a blanket reassurance tool; NICE specifically advises against imaging typical primary headaches purely for reassurance.

Frequently Asked Questions about Severe Headache