Normal causes include: Tension, fatigue, hunger, caffeine withdrawal or spending time in a hot, stuffy room. These headaches are bothersome but not dangerous.
When to get help:
You suddenly develop a persistent, extremely painful headache on one side of your head that feels different from prior headaches. This may be temporal arteritis, an inflammation that can be cured with corticosteroids. Left untreated, it can progress to blindness.
If the headache is sudden and severe with no known cause, you may be having a stroke or a brain aneurysm. Call 911 now.
If you have a combination of headache, fever and stiff neck, you may have viral or bacterial meningitis. Go to the emergency room. Viral meningitis gets better on its own in about a week, but bacterial meningitis can cause permanent brain damage or death if it’s not diagnosed and treated early.
In addition, if you get an aura—a short-lived sensory disturbance that causes visual effects or tingling—or if the headache affects only one side of your head, makes you nauseated or lasts much of the day, check with your doctor to see if you’re having a migraine. Migraines aren’t always an emergency, but your doctor may be able to treat them.