A few initial signs of hyperglycemia could be glycosuria (glucose in the urine), polyuria (increased volume of urine), polydipsia (extreme thirst), vision disturbances, and mental status changes like confusion or lethargy.Commonly in women, yeast like vaginal infections are a first sign of hyperglycemia because the bacteria in the vagina thrive on the high blood glucose concentrations. These women may only seek treatment with their physician after repeated attempts at home, to cure, what they think, is a yeast infection.

In hyperglycemia, the kidney's ability to conserve glucose is exceeded, this causes a "spilling" of glucose into the urine. Total body water follows glucose into the urine by osmosis causing the person to void a greater volume and with more frequency. Because the person is voiding more than usual, extreme thirst may follow. A common complaint is that they are drinking fluids all the time but are still thirsty. Depending on how high the blood sugar gets, the person may become confused and disoriented or extremely lethargic.