Long-term complications

Untreated hyperglycemia can cause long-term complications. These include:

  • Cardiovascular disease
  • Nerve damage (neuropathy)
  • Kidney damage (diabetic nephropathy) or kidney failure
  • Damage to the blood vessels of the retina (diabetic retinopathy), potentially leading to blindness
  • Clouding of the normally clear lens of your eye (cataract)
  • Feet problems caused by damaged nerves or poor blood flow that can lead to serious infections, and in some severe cases, amputation
  • Bone and joint problems
  • Skin problems, including bacterial infections, fungal infections and nonhealing wounds
  • Teeth and gum infections

Emergency complications

If blood sugar rises high enough or for a prolonged period of time, it can lead to two serious conditions.

  • Diabetic ketoacidosis. Diabetic ketoacidosis develops when you don't have enough insulin in your body. When this happens, sugar (glucose) can't enter your cells for energy. Your blood sugar level rises, and your body begins to break down fat for energy.

    This process produces toxic acids known as ketones. Excess ketones accumulate in the blood and eventually "spill over" into the urine. Left untreated, diabetic ketoacidosis can lead to a diabetic coma and be life-threatening.

  • Hyperglycemic hyperosmolar syndrome. This condition occurs when people produce insulin, but it doesn't work properly. Blood glucose levels may become very high — greater than 600 mg/dL (33 mmol/L). Because insulin is present but not working properly, the body can't use either glucose or fat for energy.

    Glucose is then spilled into the urine, causing increased urination. Left untreated, diabetic hyperglycemic hyperosmolar syndrome can lead to life-threatening dehydration and a coma. Prompt medical care is essential.

April 18, 2015