How can you tell if you have diabetes? Most early symptoms are from higher-than-normal levels of glucose, a kind of sugar, in your blood. The warning signs can be so mild that you don’t notice them. That’s especially true of type 2 diabetes. Some people don’t find out they have it until they get problems from long-term damage caused by the disease. With type 1 diabetes, the symptoms usually happen quickly, in a matter of days or a few weeks. They’re much more severe, too.