Diabetes affects 24 million people in the U.S., but only 18 million know they have it. About 90% of those people have Type 2 diabetes. In diabetes, rising blood sugar acts like a poison. diabetes is often called the silent killer because of its easy-to-miss symptoms. "Almost every day people come into my office with diabetes who don't know it," says Maria Collazo-Clavell, MD, an endocrinologist at the Mayo Clinic in Rochester, Minn. The best way to pick up on it is to have a blood sugar test. But if you have these symptoms, see your doctor. Watch the video: 5 Ways to Prevent Type 2 Diabetes