What should you know about sudden sleepiness and headache?

A blocked or inflamed nose and sinuses can create head pressure and disturb sleep; see Allergic Rhinitis or Chronic Sinusitis for related patterns. A Common Cold or COVID-19 may bring headache, tiredness, fever, cough or congestion. Dehydration and Heat Exhaustion are more likely after sweating, hot surroundings, vomiting or diarrhoea. Dengue Fever can cause headache with fever, marked aches or a rash, especially after mosquito exposure. Anxiety can make sleep feel unrefreshing and may accompany tension-type headache, but new or unusual symptoms should not be dismissed as stress.

Stop driving and sit or lie somewhere cool and safe while you judge how alert you feel. Sip water or an oral rehydration drink if you can swallow normally, and rest away from bright screens. Check your temperature if possible and note when the sleepiness began, the headache location, recent heat exposure, illness, sleep loss, medicines and fluid intake. Do not drink alcohol or take more medicine than the label allows. Arrange medical advice if the symptom is new, keeps returning, or does not settle with rest and fluids.

Get emergency help for a sudden severe headache, confusion, fainting, a seizure, trouble speaking, new weakness or numbness, vision loss, breathing difficulty, repeated vomiting, a stiff neck with fever, or sleepiness so strong that you cannot stay awake. Seek urgent assessment after a head injury or when headache and drowsiness worsen quickly. Do not drive yourself; have someone stay with you.

Could dehydration, infection, heat exposure, a medicine or a sleep problem explain this combination? Which warning signs should make me seek urgent help? Do I need an examination, blood tests or another check if it returns?