Headaches can be a pain — literally. They’re often the body’s way of telling us that something isn’t quite right. Maybe we’re dehydrated, hungry or lacking sleep. While a bad headache can be brought on by something fairly simple, such as dehydration or fatigue, it could also be a sign of something more serious. If you’ve suffered from headaches or migraines for years, it may be difficult to recognize when something bigger is happening.

Before reaching for some medicine, you may want to take the time to notice your symptoms, to make sure there isn’t something more serious going on. Knowing what type of headache you are experiencing can allow you to treat it correctly. There are several warning signs that often accompany headaches when something bigger is going on. Here are the types of headaches you should watch out for:

1. Cluster Headache

Cluster headaches are less common than migraines or tension headaches. They usually occur over one eye, and they affect more men than women. A cluster headache can appear suddenly and cause a severe, debilitating pain on one side of the head. This type of headache is recurring, and sufferers may experience an episode several times a day during a period of time that can range anywhere from two weeks to three months.

Warning Signs

Cluster headaches can be managed, but there are warning signs to look for. If you’re suffering from cluster headaches and you notice your eye turning red, or the pain is so severe that it’s affecting your ability to function, it’s time to see a doctor. An aneurysm can start with a sudden severe headache, which may be accompanied by neck stiffness and intolerance of bright light.

2. Thunderclap Headache

Thunderclap headaches are true to their name — they grab your attention like a sudden clap of thunder. The pain of these sudden and severe headaches peaks within a minute of onset, and they may start fading after about an hour. About 80% of those who experience a thunderclap headache have a triggering event, such as exercise or sexual activity – something that had their blood pumping.

Warning Signs

A thunderclap headache can be a warning sign of something potentially life-threatening. It could indicate bleeding in the brain, a stroke, aneurysm or a brain tumor. If you experience a thunderclap headache, go get things checked out by a doctor.

3. Headache After a Head Injury

At one point or another, we’re probably all going to get hit in the head with something. Whether it’s a basketball, a Frisbee or a low-hanging light, we’ll all experience a bump on the head on occasion. Depending on how severe your injury is, it could disrupt the normal function of the brain. If your injury is serious enough to cause a concussion, you need to see a doctor.

Warning Signs

Symptoms of a concussion might not start right away. They could start days or even weeks after a head injury. These symptoms can include a headache, neck pain, nausea, dizziness and fatigue. A brain injury can be extremely serious. If there’s even a chance of brain injury or a concussion, you’ll want to take a trip to the hospital.

Other Signs and Symptoms to Look Out For

  • Headaches that first develop after the age of 50
  • Headaches with a sudden change in frequency, location or severity
  • Headaches that get worse over time
  • Headaches that cause weakness
  • Headaches that affect your vision or speech

h/t: the hearty soul