When a headache is an emergency: warning signs to know

A headache that does not feel like your usual one can be frightening. You may wonder if you are overreacting, or if you should wait until morning. This page is meant to help you decide quickly and calmly. It lists the warning signs that doctors and health services use, in two groups: act now, and see a doctor soon.

First, some perspective

A 2019 review in the journal Neurology (Do and colleagues) notes that a minority of people with headache have a 'secondary' headache, meaning one caused by another condition. The authors note that estimates of how many headaches are secondary depend on the setting (for example 18% in one estimate, lower in some clinics). The review set out the SNNOOP10 list of 'red and orange flags' to help doctors decide who needs closer checking. A flag does not mean something serious is present. It means a doctor should take a closer look.

The lists below draw on the NHS, NICE (the UK clinical guideline CG150), that review and other clinic sources. The NHS uses the UK number 999. Where you are, call 112 for emergency help.

Get emergency help now

The NHS, NICE and the other sources listed below point to the following as reasons for emergency help. Do not drive yourself. Ask someone to take you or call an ambulance, and bring any medicines you take.

• A sudden headache that is extremely painful. This is often called a 'thunderclap' headache. The International Headache Society defines abrupt onset as reaching maximum intensity in under a minute, and NICE's guideline uses 'within 5 minutes'. It can be a sign of bleeding around the brain (subarachnoid haemorrhage), according to the NHS.
• 'The worst headache of my life', or a new kind of pain you have never felt before, or pain that keeps worsening after treatment (Cleveland Clinic).
• Fever with a stiff neck, a severe headache, discomfort looking at bright light, vomiting or confusion. These can be signs of meningitis, which the NHS says can be life-threatening if not treated quickly.
• A rash that does not fade when a glass is pressed against it (NHS).
• New weakness or numbness in the face, arm or leg, especially on one side, or a drooping face.
• Trouble speaking, slurred speech, trouble walking or balancing, or trouble remembering things.
• Loss of vision, blurred or double vision that is new.
• Drowsiness, confusion, or a change in personality.
• A seizure (fit).
• A head injury. The NHS lists a head injury within the last 3 months as a reason to go to emergency with a headache.
• Sudden, intense eye pain with a red eye, blurred vision, and seeing rainbow-coloured circles around lights. The NHS says sudden glaucoma symptoms are a medical emergency.

See a doctor soon

These signs are not always an emergency, but they should not be left. The NHS says to ask for an urgent appointment, or get urgent advice, for several of them. In practice, that means seeing a doctor promptly, ideally the same day, or going to a hospital emergency department if you are worried or it gets worse.

• A headache with vision or eye problems (sudden loss of vision belongs in the emergency list above).
• In a child, a headache that is getting worse or wakes them at night (NHS).
• A headache that is triggered or made worse by coughing, sneezing, bending down or exercise (NHS, NICE).
• A headache that changes with posture, such as being worse when you stand or when you lie down (NICE calls this 'orthostatic').
• A headache with vomiting that has no other obvious reason.
• A headache that keeps getting worse, or a clear change in your usual headache pattern (NICE: 'a substantial change in the characteristics').
• A headache with jaw pain when eating or talking, a sore or tender scalp, or vision trouble. The NHS says these can be signs of temporal arteritis (giant cell arteritis), which can lead to stroke and blindness if not treated quickly. It says to ask for an urgent GP appointment or get help from NHS 111, and to be seen the same day at a hospital eye department if you have vision problems. Do not wait for the next routine appointment.
• A new kind of headache that begins later in life. The 2019 Neurology review lists onset after age 65 as a flag: in the data it cites, serious secondary causes were found in 15% of people aged 65 and over, against 1.6% of younger people. A New Zealand clinical journal (bpac) says giant cell arteritis usually affects people over 50 and that any new or new-type headache in someone over 50 should be treated as a red flag. NICE does not give an age cut-off. If you are over 50 and have a new headache, see a doctor soon.
• A new headache if you have weak immunity (for example HIV, or immune-suppressing medicines), or a history of cancer that can spread to the brain (NICE). NICE also lists a cancer history in someone under 20. If you have any cancer history, mention it and ask a doctor.
• A headache that comes with fever and gets worse, even without a stiff neck.
• A headache that started or worsened soon after you began a new medicine (Neurology review).

Pregnancy and after delivery

The NHS says to ask for an urgent appointment or call NHS 111 if you have a migraine and you are pregnant or have just had a baby. The Neurology review explains why: the chance of a secondary headache is higher in pregnancy and the weeks after birth, particularly in the third trimester. In one study of 140 pregnant women who went to acute care with headache, about a third had a secondary cause. Warning features included no earlier headache history, seizures, high blood pressure or fever. If you are pregnant and have a bad or unusual headache, contact your doctor or maternity unit promptly. Ask a doctor or pharmacist before taking any medicine.

If you already live with migraine

Having migraine does not protect you from other causes. Cleveland Clinic says it helps to know what a usual migraine is like for you, so you can notice one that is different. It advises going to emergency for a new level of pain you have not felt before, a sudden pain that reaches its peak all at once, confusion, speech trouble or vision changes you have not had before, neck stiffness, numbness or weakness, or fever.

The NHS also says to seek urgent advice if a migraine attack lasts longer than 72 hours or aura symptoms last longer than an hour at a time.

What to do while you wait for help

• Call 112 or ask someone to take you. Do not drive yourself (NHS).
• Tell someone near you what is happening and ask them to stay with you.
• Note when the headache began and what else you noticed. This helps the doctors.
• Bring your medicines, or a list of them (NHS).
• Do not give a child aspirin. The NHS says it should not be given to children aged 15 or under because of the risk of Reye's syndrome.

When headaches make you anxious

After a scare, or when you live with frequent headaches, it is common to keep scanning your head for the next sign. That worry is understandable. It does not mean every headache is an emergency, and it does not replace a doctor's advice. A short grounding exercise may help your body settle once you have followed the guidance above and you are safe.