Diabetes Symptoms The two types of diabetes have very similar symptoms. The first symptoms are related to the direct effects of high blood sugar levels. When the blood sugar level rises above 160 to 180 mg/dL, sugar spills into the urine. When the level of sugar in the urine rises even higher, the kidneys excrete additional water to dilute the large amount of sugar. Because the kidneys produce excessive urine, people with diabetes urinate large volumes frequently (polyuria). The excessive urination creates abnormal thirst (polydipsia). Because excessive calories are lost in the urine, people lose weight. To compensate, people often feel excessively hungry. Other symptoms include blurred vision, drowsiness, nausea, and decreased endurance during exercise. Type 1 : In people with type 1 diabetes, the symptoms often begin abruptly and dramatically. A condition called diabetic ketoacidosis may quickly develop. Without insulin, most cells cannot use the sugar tha...