Sudden headache: what to know

Headache can develop with dehydration, heat exhaustion, a common cold, COVID-19, allergic rhinitis or chronic sinusitis. Anxiety, missed meals, poor sleep, bright light and muscle tension may also contribute. The location, speed of onset, severity, duration and associated symptoms are more useful than the word sudden alone. Dengue fever can include headache with fever and significant body aches after possible exposure. A headache is not enough to identify any one condition.

Record what you were doing when it began, how quickly it reached its worst point, where it hurts, and whether you have fever, neck stiffness, vomiting, weakness, numbness, confusion, vision change, speech trouble or a recent injury.

Pause strenuous activity, move to a cool quiet place and drink fluids if you can. Eat if you have missed a meal. Reduce screen brightness and rest your eyes. If you use an over-the-counter pain medicine, follow the label and check with a pharmacist if pregnant, taking other medicines or managing liver, kidney or stomach disease. Avoid repeatedly taking painkillers without advice, because frequent use can perpetuate headaches. Arrange an appointment if headaches recur, change pattern or interfere with normal life.

Call emergency services for a headache that reaches extreme intensity immediately, follows a head injury, or comes with weakness, numbness, trouble speaking, confusion, seizure, fainting, severe vision change, stiff neck, high fever or repeated vomiting. Seek urgent advice for headache during pregnancy or after delivery, with very high blood pressure, or after travel with fever and body aches. Do not drive yourself if you feel confused or have neurological symptoms.

Ask whether the onset and associated symptoms call for same-day assessment, whether your medicines could contribute, and how to keep a headache diary. Share recent illness, heat exposure, hydration, sleep, meals, injury, pregnancy status, travel and any neurological changes.