OCtober 25, 2025
In most cases a headache is harmless and passes on its own, but sometimes this symptom can be a warning signal of a serious condition in the body. If the pain starts suddenly, is severe or is accompanied by other neurological signs, that is considered a reason to see a doctor. The situations in which a headache is regarded as dangerous are called “red flag symptoms”.
Sudden and very severe headache
If the pain begins all at once, like a “thunderclap”, and is very severe, this may be a sign of bleeding in the brain or of a ruptured blood vessel (for example, a subarachnoid haemorrhage). In such cases the pain reaches its peak within seconds and the patient describes it as “the worst pain I have ever felt in my life”. This situation requires emergency medical care.
Pain that appears after an injury
Pain that appears after a head injury or a fall needs particular attention. If the pain comes with dizziness, vomiting, memory loss, blurred vision or loss of consciousness, it may be related to concussion or internal bleeding. In such cases a doctor must examine you immediately.
Pain that builds up gradually and persists
If a headache builds up gradually over days or weeks, does not respond to ordinary painkillers and keeps getting stronger, this may point to a space-occupying lesion in the brain (a tumour, a vascular aneurysm and so on) or to raised pressure. Persistent pain that becomes worse at night deserves particular attention.
Pain accompanied by neurological signs
If one or several of the following symptoms occur together with the headache, this may indicate a serious disorder of neurological origin:
Loss of vision or double vision
Difficulty speaking or trouble finding words
Numbness or weakness in an arm, a leg or one side of the body
Clouding or loss of consciousness
Loss of balance and difficulty with coordination
In such cases the pain may be caused by a stroke, a transient ischaemic attack (mini-stroke), spasm of the cerebral blood vessels or another neurological disease.
Headache that starts at an atypical age
If a severe and persistent headache appears for the first time after the age of 50, it must be investigated. In older people such pain is often linked to temporal arteritis (inflammation of the blood vessels), a hypertensive crisis or a cerebrovascular disorder. In these cases laboratory tests and a Doppler ultrasound examination are essential.
Pain together with a raised temperature and a stiff neck
If the headache comes with fever, chills, neck stiffness, sensitivity to light and vomiting, this indicates an infection of the central nervous system such as meningitis or encephalitis. The patient must be admitted to hospital immediately.
Pain related to the eyes and the nose
If pain in the forehead and around the eyes is accompanied by a blocked nose or nasal discharge, this may be related to sinusitis or raised pressure inside the eye (glaucoma). Blurring of vision and haloes around lights call for an urgent ophthalmological examination.
Pain related to overuse of medication
Long-term and frequent use of painkillers (more than 10–15 times a month) can lead to medication-overuse headache. In this case the pain becomes more frequent and more persistent. In such a situation painkillers should be reduced gradually and stopped under a doctor's supervision.
Pain in women related to hormonal changes
Headaches that arise during menstruation, pregnancy or the menopause are most often related to hormonal changes. However, if the pain is severe and persistent and comes with visual disturbance, further examination may be needed.
Pain when blood pressure changes sharply
High blood pressure (particularly readings above 180/110 mmHg) increases the strain on the blood vessels in the brain and causes headache. If the pain comes with blurred vision, vomiting, ringing in the ears or dizziness, this may be a hypertensive crisis and it requires emergency medical care.
Pain that recurs regularly
If a headache is long-standing and recurrent (for example, if it occurs in the same way several times a month), this points to chronic neurological syndromes such as migraine, tension-type headache or cluster headache. In this case, instead of taking medication on your own, you should see a neurologist.
When you should call emergency help
If the pain is sudden and very severe
If there is loss of consciousness, paralysis, or disturbance of speech or vision
If the pain appeared after an injury
If it comes together with fever and a stiff neck
If the pain keeps getting worse and interferes with daily activities
In such cases losing time can be life-threatening. To rule out dangerous conditions it is important to see a doctor and to have the necessary examinations.