It is not clear why some people have symptoms of type 2 diabetes, such as increased thirst, frequent urination, excessive hunger, and fatigue, before diagnosis and others do not. Some possible explanations are:

• In type 2 diabetes, blood sugar levels rise gradually over years. If the symptoms are mild, the person may not notice them.
• People with type 2 diabetes often have complications from the disease at the time of diagnosis. It may be that there is a range of blood sugar levels within which complications arise, but the levels aren't high enough to cause symptoms.
• People differ in their awareness of symptoms.