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Dr. Chrysoula I. Liakou MD, PhD
- Treated online: Assessment online. A thunderclap headache happening now needs 112, not a video call; a doctor by video can help afterwards, or judge whether a past sudden headache still needs urgent tests.
- What it is: a sudden, severe headache that reaches its worst within a minute, or within 5 minutes at most, and lasts at least 5 minutes. People often call it the worst headache of their life.
- The main cause to rule out: bleeding around the brain (subarachnoid haemorrhage), usually from a burst aneurysm. Most people with a thunderclap headache do not have one, but only hospital tests can tell.
- How common: fewer than 50 in every 100,000 adults have a thunderclap headache each year.
- Emergency: call 112 now for a sudden, severe headache, even if it is starting to ease, and do not drive yourself.
Do not book a video appointment if you have, or have just had, a sudden, severe headache that reached its worst within a few minutes, with or without neck pain, being sick, confusion, weakness or problems with your vision. Call 112 or go to an emergency department now, and do not drive yourself. This applies even if the headache has started to ease.
Can an online doctor help with a thunderclap headache?
No, a thunderclap headache cannot be assessed or treated online while it is happening. Call 112 or go to an emergency department, because only a brain scan, and sometimes a lumbar puncture, can show whether there is bleeding around the brain. What a doctor by video can do is go through a sudden headache you had in the past and tell you how urgently you still need tests, and support you after a hospital assessment: what the results mean, substances and medicines to avoid, and headaches during sex or exercise that have already been checked.
How an online consultation helps after a sudden headache
- Urgency made clear: If a sudden headache has not been checked, the doctor tells you to go to hospital now, and what to tell the staff.
- After the hospital: What your scan and other results mean, what happens next, and when to go back.
- Triggers reviewed: Substances such as cannabis, cocaine and stimulants can narrow the brain’s blood vessels, and the doctor goes through what you take.
- Sex and exercise headaches: Once a serious cause has been ruled out, a plan to prevent them coming back.
What the doctor checks in an online assessment after a sudden headache
The doctor first decides whether you need an emergency department straight away. The doctor asks about:
- How fast it started: whether the pain reached its worst within seconds or a few minutes, and how long ago that was.
- What came with it: neck pain or stiffness, being sick, sensitivity to light, confusion, fainting, a seizure, weakness, or vision problems.
- What you were doing: sex, exercise, straining, coughing, or a fall or blow to the head.
- Whether it has been checked: a CT scan, a lumbar puncture or other tests, and their results.
- Your health: high blood pressure, pregnancy or a recent birth, a family history of brain aneurysms, and all medicines and drugs, including cannabis, cocaine and stimulants.
If a sudden, severe headache has not been checked in hospital, you will be told to go now, even if it has eased. If you have already been checked, have your discharge letter to hand for the call.
What is a thunderclap headache?
A thunderclap headache is a sudden, extremely painful headache that is at its most intense from the start, like a clap of thunder. Doctors define it by how fast it peaks: within a minute in the international headache classification, and within 1 to 5 minutes in UK guidance. The pain lasts at least 5 minutes and usually fades within a few hours.
What does a thunderclap headache feel like?
People often describe it as the worst headache of their life. It can be felt anywhere in the head and sometimes spreads down the back of the neck. It may come with:
- feeling or being sick
- a stiff or painful neck, and sensitivity to light
- confusion, drowsiness or fainting
- a seizure
- numbness, weakness, a drooping face, slurred speech or changes in vision
Thunderclap headache or ice pick headache?
Ice pick headaches are brief, sharp, stabbing pains that last seconds, often come in clusters, and are common in people with migraine or cluster headaches. A thunderclap headache lasts longer, is severe from the start, and does not usually come in repeated bursts. Brief stabbing pains are covered on the headache behind the eyes page.
What causes thunderclap headaches?
Some thunderclap headaches have no cause that can be found, but others are a sign of a serious problem, usually bleeding in or around the brain. Because no one can tell them apart at the start, every first thunderclap headache needs emergency tests. The causes include:
Swipe sideways to compare →
| Cause | What happens | Good to know |
|---|---|---|
| Subarachnoid haemorrhage | Bleeding in the space around the brain, most often from a burst aneurysm | The most common serious cause; a family history of aneurysms may raise the risk |
| Reversible cerebral vasoconstriction syndrome (RCVS) | The brain’s blood vessels suddenly narrow | The second most common cause; linked to substances such as cannabis, cocaine and stimulants; the vessels usually return to normal |
| A tear in an artery to the brain (dissection) | The lining of a neck or brain artery tears | Can follow an injury or whiplash |
| Bleeding in the brain, or a stroke | A burst or blocked blood vessel | More likely with uncontrolled high blood pressure |
| A blood clot in a brain vein | Cerebral venous thrombosis | Can follow an injury or some hormone medicines |
| A sudden, severe rise in blood pressure | A hypertensive crisis | Needs emergency treatment |
| Pregnancy complications | Eclampsia, or bleeding in the pituitary gland during or after pregnancy | Any sudden, severe headache in or after pregnancy needs 112 |
| Other causes | Meningitis or encephalitis, a leak of spinal fluid, a severe sinus infection with pressure changes | Found on tests in hospital |
| No cause found (primary thunderclap headache) | A severe, sudden headache with normal tests | Diagnosed only after a serious cause has been ruled out |
What happens if you ignore a thunderclap headache?
Some of the causes can be fatal without prompt treatment. Bleeding around the brain can cause lasting disability, and recovery can take months or years, which is why speed matters. Most people with a thunderclap headache do not turn out to have a bleed, but there is no way to know without tests, and a sudden headache that has eased can still be a warning sign.
Can a thunderclap headache kill you?
The headache itself does not, but some of its causes can, especially bleeding around the brain. When tests find no serious cause, people usually return to normal activities once the headache passes.
How is a thunderclap headache diagnosed?
In hospital, a senior doctor takes a careful history, especially how fast the headache started and how long it took to peak, then arranges tests:
- A CT scan of the head without dye. It is most accurate within 6 hours of the headache starting, and shows blood around the brain if there is a bleed.
- A lumbar puncture if the CT scan is normal but was done more than 6 hours after the start. It is done at least 12 hours after the headache began, and the fluid is checked for signs of bleeding.
- Scans of the blood vessels, such as a CT angiogram or an MRI and MR angiogram, to find an aneurysm, a tear, narrowing of the vessels or a clot.
If you cannot describe what happened, someone who saw the headache start can help. Tell the staff the exact time it began.
What can be mistaken for a thunderclap headache?
Swipe sideways to compare →
| Headache | How it starts and how long it lasts | What to do |
|---|---|---|
| Thunderclap headache | Severe from the start, peaking within a minute; lasts at least 5 minutes | Call 112 |
| Ice pick headache | Stabbing pains lasting seconds, often in clusters | See a doctor if new |
| Migraine | Throbbing, with sickness and light sensitivity, for 4 to 72 hours | See a doctor; a first ‘worst ever’ headache needs 112 |
| Cluster headache | Severe pain around one eye for 15 to 180 minutes, with a red, watering eye | See a doctor |
| Sex or exercise headache | During sex or strenuous exercise; can be sudden and explosive | A first one needs 112 |
Headaches during sex or exercise
Some sudden headaches are set off by sex or strenuous exercise. A first one must be treated like any thunderclap headache, because bleeding around the brain, a torn artery and narrowing of the blood vessels have to be ruled out. Once these have been ruled out:
- Sex headache: a dull ache on both sides of the head that builds with arousal, or a sudden, explosive pain just before or at orgasm. It lasts from 1 minute to 24 hours, is more common in men, and in up to 40% of people keeps coming back for more than a year.
- Exercise headache: brought on by strenuous exercise, especially in hot weather or at altitude, and lasting less than 48 hours.
- Repeated explosive headaches are treated as reversible cerebral vasoconstriction syndrome until tests show otherwise.
Headaches that keep coming back with sex over a long period are much less likely to be dangerous, but a new or different one still needs urgent checks.
What might the doctor recommend after a sudden headache?
What happens next depends on whether the headache has been checked in hospital. This is the framework the doctors use, in line with NICE guidance:
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| What you have | Likely first step | Suitable for online care? | When in-person care is needed |
|---|---|---|---|
| A sudden, severe headache now | Emergency assessment and a CT scan | No | Call 112 now |
| A sudden, severe headache earlier, not yet checked, even if it has eased | Emergency assessment | No | Go to an emergency department now |
| Checked in hospital, no cause found | Follow-up, and a plan if it comes back | Yes | If a new sudden headache comes |
| Diagnosed with reversible cerebral vasoconstriction syndrome | Avoiding substances that narrow blood vessels, and specialist follow-up | Partly | For follow-up scans |
| Sex or exercise headaches, already checked | An anti-inflammatory painkiller before activity, or prevention | Yes | If the headache changes |
| After treatment for a bleed around the brain | Support with recovery, headaches and mood, alongside the specialist team | Partly | For specialist reviews |
Had a sudden, severe headache that was never checked? A doctor can tell you in one consultation how urgently you need tests.
See available times →How is a thunderclap headache treated?
Treatment depends on the cause, and it starts in hospital. A burst aneurysm is usually treated with surgery to stop the bleeding, either by clipping it or by sealing it from inside the blood vessel (coiling), along with medicines for pain, blood pressure and blood flow. When no serious cause is found, the headache is treated with medicine such as an anti-inflammatory painkiller.
What you can do yourself
- Call 112 straight away for a sudden, severe headache, and do not drive yourself.
- Note the exact time the headache started, and how fast it reached its worst.
- Take a list of your medicines, and tell the staff about any drugs you have taken.
- Afterwards, avoid cannabis, cocaine and stimulants, which can narrow the brain’s blood vessels.
- Keep your blood pressure under control, stop smoking, eat well and stay active.
Prescription treatment
A prescription is never issued without a consultation. The cause of a thunderclap headache is treated in hospital. Once a serious cause has been ruled out, and if headaches come predictably with sex or exercise, the doctor may prescribe an anti-inflammatory painkiller, such as indomethacin, to take beforehand, or discuss a daily preventive medicine if they are frequent. Codeine and other opioids are never prescribed online. If the doctor prescribes, use the prescription at a pharmacy near you.
What does not help
Taking painkillers and waiting to see if a sudden, severe headache settles. Driving yourself to hospital. Assuming a first ‘worst ever’ headache is a migraine.
Special situations
Pregnancy and after giving birth
A sudden, severe headache in pregnancy or after giving birth can be a sign of eclampsia or bleeding in the pituitary gland: call 112.
A family history of brain aneurysm
A family history of aneurysms may increase the risk of a bleed, so tell the doctor and the emergency staff about it.
While travelling in Europe
Strenuous exercise in heat or at altitude can bring on exercise headaches, but a first sudden, severe headache abroad is treated the same way: call 112. Keep a copy of any hospital discharge letter for your own doctor.
Children
Mobi Doctor consultations are for adults aged 18 and over. A child who is unwell needs a paediatrician or a local doctor in person, and emergency signs in a child mean 112.
When a thunderclap headache is assessed online, and when you need in-person care
Assessed online: a sudden headache in the past where it is unclear whether tests are still needed, follow-up after a hospital assessment, substances and medicines to avoid, and sex or exercise headaches that have already been checked.
In-person care: every thunderclap headache happening now, every sudden, severe headache that has not been checked, scans and lumbar punctures, and the treatment of any cause found.
When to get in-person care
Call 112 or go to an emergency department now for:
- a sudden, severe headache that reaches its worst within 5 minutes, even if it starts to ease
- a sudden headache with neck pain or stiffness, being sick or sensitivity to light
- a headache with confusion, drowsiness, fainting or a seizure
- a headache with numbness or weakness, a drooping face, slurred speech, or loss of vision
- a headache with a high temperature and a stiff neck, or a rash that does not fade when a glass is rolled over it
- a headache after a head injury
- a first sudden, severe headache during sex or exercise
- a sudden, severe headache in the past few days that was never checked, even if it has gone
Get medical advice the same day for:
- a headache triggered or made worse by coughing, sneezing, bending down or exercise that has not been checked before
- a headache with vomiting
- headaches with sex or exercise that have changed since they were last checked
How Mobi Doctor works
- Book a time that suits you: daily 7am–11pm CEST. You can see a doctor over video, usually within 15 minutes. No subscription, and the exact price is shown before you pay.
- Speak to a licensed doctor about the headache: say when it happened, how fast it reached its worst and what you were doing, and share any hospital results. A headache happening now needs 112.
- Leave with a plan: what to do, what to take and for how long, and which signs mean you should be seen in person. If the doctor prescribes, use the prescription at a pharmacy near you.
No sign-up needed
A sudden, severe headache happening now needs 112. For a past headache, tick every symptom you have to see each condition page that mentions it. It finds the right page, not a diagnosis: a doctor gives you that on a video call.
Tap the body — an area or a point — to browse symptoms anywhere
Not sure this is the right page? Look up any symptom in the full symptom checker, or book and describe it to a doctor.
Frequently asked questions about thunderclap headaches
What is a thunderclap headache?
A sudden, extremely painful headache that reaches its worst within a minute, or within 5 minutes at most, and lasts at least 5 minutes. It can be a sign of bleeding around the brain, so it always needs emergency care: call 112.
What does a thunderclap headache feel like?
Like a clap of thunder: severe from the start, often described as the worst headache of your life. It can come with neck pain, being sick, sensitivity to light, confusion, a seizure, weakness or vision changes.
How long does a thunderclap headache last?
A thunderclap headache lasts at least 5 minutes by definition and usually fades within a few hours, although a dull headache can linger for days; the speed of onset, not the length, is what makes it dangerous, so a headache that peaked within a minute needs emergency tests even if it has eased or gone by the time you reach hospital, because a small warning bleed can be followed by a larger one within days.
What causes thunderclap headaches?
The most common serious cause of a thunderclap headache is bleeding around the brain, usually from a burst aneurysm. Others include sudden narrowing of the brain’s blood vessels, a torn artery, a clot in a brain vein, a severe rise in blood pressure and pregnancy complications. Sometimes no cause is found.
What happens if you ignore a thunderclap headache?
Some of its causes can be fatal or cause lasting disability without prompt treatment. There is no way to know the cause without tests, so call 112 even if the headache starts to ease.
What can you do yourself while waiting for help with a thunderclap headache?
Call 112 first, then sit or lie down somewhere safe, do not drive, do not take aspirin or ibuprofen, which can worsen bleeding, avoid straining, bright light and exertion, note the exact time the pain started and what you were doing, unlock the door and keep the phone close, and have someone stay with you; if you vomit, turn on your side. Nothing you can do yourself treats a thunderclap headache, so the only job is to get assessed quickly.
Can a thunderclap headache kill you?
The headache itself does not, but some of its causes can, especially bleeding around the brain. When tests find no serious cause, people usually return to normal once the headache passes.
How is a thunderclap headache diagnosed?
A thunderclap headache is investigated with a CT scan of the head, most accurate within 6 hours of the start. If it is normal but was done later, a lumbar puncture at least 12 hours after the start checks for bleeding. Scans of the blood vessels look for an aneurysm or other causes.
What can be mistaken for a thunderclap headache?
Ice pick headaches, which last seconds, migraine, cluster headache, and headaches during sex or exercise. Only tests can rule out a serious cause, so a first sudden, severe headache always needs emergency care.
Can a thunderclap headache be harmless?
Sometimes no cause is found, and it is then called a primary thunderclap headache. But this can only be decided after hospital tests have ruled out bleeding and other serious causes.
Can a thunderclap headache be prevented?
Only partly, because most come from an aneurysm or blood vessel problem nobody knew about; what lowers the risk is controlling blood pressure, not smoking, which doubles the chance of an aneurysm bleeding, limiting alcohol and avoiding cocaine and amphetamines, which trigger both bleeds and blood vessel spasm. People with a close relative who had a subarachnoid haemorrhage, or with polycystic kidney disease, can ask about screening scans, and a thunderclap headache from blood vessel spasm is prevented by avoiding the trigger drug.
Why do I get a sudden headache during sex?
Headaches during sex can build with arousal or come on suddenly at orgasm. A first one needs emergency tests to rule out bleeding or a torn artery. Once these are ruled out, they are usually not dangerous, and a doctor can help prevent them.
I had a sudden, severe headache a few days ago. What should I do?
Go to an emergency department rather than waiting, even if it has gone. A sudden headache that peaked within a few minutes needs tests, and a doctor by video can only tell you how urgently, not rule out a bleed.
Can an online doctor help with a thunderclap headache?
Not while it is happening: call 112. A doctor by video can tell you how urgently a past sudden headache still needs tests, and support you after a hospital assessment.
- Subarachnoid haemorrhage caused by a ruptured aneurysm: diagnosis and management (NG228), NICE, National Institute for Health and Care Excellence, 2022.
- Headaches in over 12s: diagnosis and management (CG150), NICE, National Institute for Health and Care Excellence, 2012, updated 2021.
- Subarachnoid haemorrhage, NHS, National Health Service (UK), reviewed 4 September 2025.
- Headaches, NHS, National Health Service (UK), reviewed 17 April 2024.
- Thunderclap headache, Cleveland Clinic (US), reviewed 12 October 2022.
- Thunderclap headaches: symptoms and causes, Mayo Clinic (US), updated 4 February 2020.
- Thunderclap headaches, American Migraine Foundation (US), 19 April 2023.
- 4.4 Primary thunderclap headache, International Classification of Headache Disorders, 3rd edition (ICHD-3), International Headache Society, 2018.
- 4.3 Primary headache associated with sexual activity, International Classification of Headache Disorders, 3rd edition (ICHD-3), International Headache Society, 2018.
- 4.2 Primary exercise headache, International Classification of Headache Disorders, 3rd edition (ICHD-3), International Headache Society, 2018.
- Cluster headaches, NHS, National Health Service (UK), reviewed 18 August 2023.
This page is for information only and is not a substitute for a medical consultation. Guideline links are provided for transparency; treatment decisions are made with your doctor.
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