Not surprisingly, a reported 65% of those US employees with low-paying jobs often go to work sick. The number for professionals and high-income employees is only slightly better at 48%. One risk is that sick and contagious employees will infect their coworkers, leading to a greater decrease in productivity. Even more terrifying, an employee who thinks they may just be suffering from a cold or the flu may come to work and have to deal with an even more serious health event.

Here are 7 symptoms that should never be ignored at work. If you’re not sure if your employee or coworker is dealing with something serious, be safe and don’t wait—call 911.

1. Chest pain doesn’t always mean a heart attack, but don’t take any chances. Some heart attacks come on suddenly, while others start slowly. Get help right away if someone feels a tightness or squeezing in the center of their chest that lasts for a more than a few minutes or stops and comes back again. They may feel pain in your back, neck, jaw, stomach, or one or both arms. They may be short of breath—with or without chest pain—or feel dizzy, sweaty, or sick to your stomach. Call 911 (don’t try to drive yourself is you are having chest pains) if you think someone may be having a heart attack and get the person to the hospital.

2. Sudden shortness of breath. Many types of work can lead to someone feeling out of breath, but sudden shortness of breath for no obvious reason can be a sign of something more serious, like a blood clot in the lungs, collapsed lung, or heart attack. Call 911 if someone you work with can’t catch their breath.

3. Sudden, intense headaches that come on out of the blue are often called thunderclap headaches. The pain usually peaks within one minute. Some people feel faint or sick to their stomach. Many thunderclap headaches are life-threatening, so call 911 right away if someone at work is having one. It could mean dangerous bleeding in or around the brain, or another problem with the brain’s blood supply.

4. Sudden confusion. We’ve all had that where’d-I-just-put-my-keys feeling. But it’s important to call 911 if someone becomes confused rapidly. It could be caused by fever, stroke, low blood sugar, or many other reasons. Watch for cold, clammy skin, faintness or dizziness, a fast pulse, headache, or fast or slow breathing. Check also to see if the confused person has diabetes or has had a brain injury.

5. Sudden or severe belly pain. Most stomach problems like indigestion or gas usually go away in a few hours. But belly pain can sometimes be serious. Take someone to an emergency room if they have severe belly pain, especially if they:

  • could be pregnant
  • also have a fever
  • have pain in the back, chest, neck, or shoulder
  • are vomiting blood or have bloody diarrhea
  • feel stiffness or tenderness in their stomach area

6. Flashes of light. Someone “seeing stars” or light flashes should see a doctor right away. These could be signs of a detached or torn retina, a serious problem that can lead to blindness if it’s not treated early and an especially risky condition to have at work. Some people also see flashes of light before a migraine headache. In very rare cases, light flashes can be a sign of cancer.

7. Signs of stroke. Think F.A.S.T and watch for:

  • Face drooping
  • Arm weakness
  • Speech problems
  • Time to call 911: If someone shows any of these symptoms, call 911 immediately, even if the symptoms stop. The sooner you get help, the better chances the person will have of surviving.