See your doctor as soon as possible if you experience any of these troubling symptoms.

We all get headaches from time to time. They can be brought on by annoying but manageable reasons such as stress, dehydration or your menstrual cycle, or they could be the result of an ongoing medical issue, such as migraines.

But how can you tell when a headache is a symptom of an even more serious or life-threatening problem? Here are some signs to look for.

1. You have speech or vision changes.

When a headache is not just a headache, you will also have other symptoms. If you also have changes in your vision, trouble speaking or walking, or weakness on one side of body, you could be having a stroke.

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A stroke occurs when the blood supply to your brain is cut off or severely reduced, causing cells to die almost immediately. Migraines with “aura” can be confused with a stroke, but they often give you added sensations, such as tingling in the body or flashes in your vision, whereas a stroke takes away sensations and results in a loss of vision or lack of feeling in the hands.

Even if you get migraines, the pain you feel from a headache during a stroke will be different — for example, a headache that comes on very suddenly is likely not a migraine and could be caused by a stroke. But it can be hard to tell the difference, so if you even suspect you may be having a stroke, call 911.

2. Your behavior changes.

If you’ve been getting worse and worse headaches and have other behavioral changes, that could be a sign of a brain tumor. Not all brain tumors are cancerous, but even benign tumors can cause serious problems.

As the abnormal cells of a tumor cause it to grow, it can press on the blood vessels in your head, causing headaches. It also can press into the brain itself, causing neurological changes, depending on where it’s situated. These changes may cause you to act differently — according to the American Brain Tumor Association, more than half of patient with malignant (cancerous) brain tumors experience behavioral changes.

You also might have problems with memory, concentration, judgment and reasoning, reading and writing, and/or emotional control. If you or others around you have noticed these changes along with your headaches, see your doctor.

3. It comes on suddenly and severely.

A brain aneurysm occurs when weak blood vessels in the brain start expanding or “ballooning” out. Usually they don’t cause symptoms, although if they get very big, they can cause headaches. But a ruptured aneurysm, which occurs when the ballooned vessel pops and leaks blood around the brain, can cause a massive, sudden headache.

“The classic presentation is the worst headache of your life,” said Jonathan J. Russin, MD, assistant professor of clinical neurological surgery at the Keck School of Medicine of USC and a neurosurgeon at Keck Medicine of USC. “They call it a ‘thunder clap’ headache.”

It may also be accompanied by nausea, vomiting, weakness or drowsiness. If you experience a major headache like this, call 911 immediately.

4. You also have a stiff neck or high fever.

If you have a headache and a fever, you may think it’s the flu. But add in the telltale symptom of a stiff neck, and you may have meningitis.

The infection, which can be bacterial or viral, affects the membranes that cover the brain and spinal cord. The swelling of these membranes is what can trigger headache and stiff neck. You may also have nausea, vomiting or even seizures if you have meningitis. Although meningitis is hard to diagnose because it can mimic other infections, if you have a headache along with these other symptoms, it’s best to get checked out by your doctor.

5. Headaches are interfering with your daily life.

If you have headaches that are landing you in bed all day or otherwise making you unable to perform your normal daily activities, it’s time to see a doctor. You may be experiencing migraines, or the headaches could be a symptom of another underlying issue such as the ones above. Only a doctor can assess the cause, so get help as soon as possible.

By Tina Donvito

Make an appointment with one of our headache specialists at Keck Medicine at USC. If you are in the Los Angeles area, schedule an appointment by calling (800) USC-CARE (800-872-2273) or by visiting neuro.keckmedicine.org/request-an-appointment.