Have you ever typed a symptom into Google, only to find everything from a harmless vitamin deficiency to a life-threatening disease? The truth is that a single symptom can have many different causes. That's why doctors don't diagnose based on one complaint—they look at the whole picture. Here are three common symptoms and three very different conditions that can cause each one. 1. Chest Pain Chest pain is one of the most alarming symptoms, but not every case is a heart attack