Causes

Blood sugar that's either too high or too low for too long may cause various serious conditions, all of which can lead to a diabetic coma.

• Diabetic ketoacidosis. If your muscle cells become starved for energy, your body may respond by breaking down fat stores. This process forms toxic acids known as ketones. If you have ketones (measured in blood or urine) and high blood sugar, the condition is called diabetic ketoacidosis. Left untreated, it can lead to a diabetic coma.

  Diabetic ketoacidosis is most common in type 1 diabetes but sometimes occurs in type 2 diabetes or gestational diabetes.

• Diabetic hyperosmolar syndrome. If your blood sugar level tops 600 milligrams per deciliter (mg/dL), or 33.3 millimoles per liter (mmol/L), the condition is called diabetic hyperosmolar syndrome.

  Severely high blood sugar turns your blood thick and syrupy. The excess sugar passes from your blood into your urine, which triggers a filtering process that draws tremendous amounts of fluid from your body. Left untreated, this can lead to life-threatening dehydration and a diabetic coma. About 25 to 50 percent of people with diabetic hyperosmolar syndrome develop a coma.

• Hypoglycemia. Your brain needs glucose to function. In severe cases, low blood sugar may cause you to pass out. Hypoglycemia can be caused by too much insulin or not enough food. Exercising too vigorously or drinking too much alcohol can have the same effect.