Sometimes, headaches can be an emergency. Here's when.

(HealthDay)—Nearly everyone has a headache now and then. Most of the time, relief is just an over-the-counter pill away. Other times, learning ways to relax and relieve tension, or getting treatment for sinus infections can get rid of your headaches.

Sometimes, though, headaches can warn of a serious health issue. High blood pressure, a stroke, a brain tumor, carbon monoxide poisoning, infections, a concussion and more could be linked to your headaches.

That's why it's important to know when to take action. Don't try to diagnose the problem. Contact your doctor or go to the emergency department and let the professionals figure it out.

Medical experts say you should consider it a headache emergency, worthy of a 911 call, if:

• You would describe the headache as the worst one you've ever had.
• Your headache came on suddenly and feels explosive.
• You have a high fever and nausea as well as a headache.
• You have slurred speech, vision changes, dizziness, confusion or inability to move your arms or legs on one side of your body.

You also have reason for concern if:

• Your headache is the first severe one you've ever had and it's limiting your ability to function.
• Your headache started right after a head injury, after strenuous exercise or even after sex.
• Your headache is extreme, and one eye looks bloodshot.
• You're older than 50 and suddenly start getting headaches for the first time in your life.
• You have a nagging headache that worsens over 24 hours.

Some headache situations might not warrant a 911 call but still merit a visit with your doctor.

That's the case if headaches wake you up from sleep, or they're worse in the morning. Another reason for checking in with your doctor: If a headache lingers for days or has no apparent cause, like tension or dehydration.

Even if you get headaches regularly, talk to your doctor if the usual pattern of your headaches—especially their intensity—changes.