Nearly 26 million Americans had diabetes in 2010, and many were not being adequately treated, according to the Centers for Disease Control and Prevention. Most people have heard about the long-term complications of poorly controlled diabetes, such as kidney failure, cardiovascular disease and blindness. People with diabetes can also develop acute complications. If your blood glucose gets too high due to inadequate treatment, or falls too low due to overly aggressive treatment, you could suddenly lose consciousness. Insulin shock, diabetic ketoacidosis and hyperglycemic hyperosmolar syndrome are all potential causes of diabetic coma.
Insulin is a hormone your pancreas normally produces in response to rising glucose levels. Many people with diabetes must take insulin to prevent their blood glucose from rising too high. If you take more insulin than your body needs, you could suddenly develop hypoglycemia, or low blood glucose. People who take insulin and exercise without eating or drink too much alcohol are particularly susceptible to hypoglycemia. Insulin shock, which is a form of diabetic coma, may occur if your blood glucose falls too low to support your brain’s metabolic demands -- usually below 50 mg/dL. Seizures may occur before the onset of coma.
Just as a low blood glucose level can trigger unconsciousness, extremely high blood glucose levels can alter brain function and lead to coma. Diabetic ketoacidosis, which usually affects people with type 1 diabetes, happens when you don’t have enough insulin in your system. DKA may be the initial manifestation of newly developed diabetes, or it may result from a skipped insulin dose in a person who has already been diagnosed with diabetes. Infections and alcohol abuse can also trigger DKA. Blood glucose levels in people with DKA are typically above 250 mg/dL, and ketones -- the byproducts of fat breakdown -- can be detected in the urine and blood of people suffering from DKA. The primary cause of coma in people with DKA is brain swelling due to severe dehydration and loss of electrolytes, which result from excessive urination caused by elevated blood glucose and ketone levels. If untreated, DKA is fatal.
Hyperglycemic Hyperosmolar Syndrome
Just as people with type 1 diabetes are susceptible to DKA, those with type 2 diabetes are at risk for hyperglycemic hyperosmolar syndrome if their diabetes is not adequately controlled. This refers to the extremely high blood glucose levels -- often above 500 mg/dL -- and dehydration that characterize this disorder. Prolonged or severe high blood glucose triggers excessive urination, which in turn leads to dehydration and loss of electrolytes. If this situation persists, your blood becomes progressively more concentrated and, mirroring the brain injury seen in DKA, you may go into a coma. Because most people with type 2 diabetes still make some insulin, they usually do not break down fat tissue or produce large amounts of ketones when their diabetes is uncontrolled. So, hyperglycemic hyperosmolar syndrome is often called nonketotic hyperosmolar syndrome. The fatality rate in nonketotic hyperosmolar syndrome can be as high as 40 percent.
Brain dysfunction and coma can occur in people who are either hypoglycemic or hyperglycemic. For people who use insulin, coma can result from taking too much insulin or from forgetting to take one or more doses of insulin. People with diabetes who do not use insulin may become comatose as the result of high doses of oral medications or from not sticking to their treatment plan. A person with diabetes who becomes confused, disoriented or has other neurological symptoms should seek immediate medical attention. If a person with diabetes becomes unconscious, it is a medical emergency.
- Centers for Disease Control and Prevention: National Diabetes Fact Sheet, 2011
- American Family Physician: Insulin Management in Type 2 Diabetes Mellitus
- The Merck Manual of Diagnosis and Therapy, 18th Edition; Mark H. Beers, M.D.
- American Family Physician: Diabetic Ketoacidosis
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