You should call 911 or come right to the emergency room if you are systemically sick. That's when an illness affects your entire body, and you have severe pain or sudden onset of severe symptoms, a fever that won't break, or "something doesn't work", like you're unable to move an arm or leg or breathe normally

Typical conditions treated:

• Chest pain or pressure
• Compound fracture
• Head injuries
• Seizures
• Shortness of breath
• Uncontrolled bleeding