Brittle diabetes—also called labile diabetes—is a rare but serious form of the disease in which there are dramatic and often unpredictable fluctuations in blood sugar levels.

Blood sugar naturally rises and falls throughout the day in response to meals, exercise and other factors. The cornerstone of good diabetes control is maintaining blood sugar within a tight range, to mimic that of people without the disease, but brittle diabetes can make this very difficult. Blood sugar spikes very high or drops too low and not necessarily in sync with the factors that normally affect it. In fact, the blood sugar fluctuations in brittle diabetes are so dramatic that medical attention and frequent hospitalizations are often required. As a result, people with brittle diabetes often experience significant disruption of their daily lives and psychological stress. However, the life expectancy of people with brittle diabetes is no different from those who don’t suffer from the condition.

Brittle diabetes is more likely to occur in people with type 1 diabetes mellitus (one percent of people with type 1 diabetes who use insulin have brittle diabetes), but it can be found in some people with type 2.

Why does this disease occur? It’s usually because the individual isn’t able to mimic the pancreas’s finely tuned production and release of insulin with the injectable version of the hormone. Additional causes may include diabetic gastroparesis, a condition in which the stomach doesn’t move food down toward the intestines at a normal rate, causing a delay in the delivery of glucose to the cells, and certain endocrine disorders like hypothyroidism.

People with brittle diabetes generally have one of the following three presentations:

  1. Predominant hyperglycemia (high blood sugar) with recurrent ketoacidosis (a condition in which compounds called ketones build up in the blood). In these individuals, symptoms often include excessive thirst, frequent urination, nausea, vomiting, abdominal pain, shortness of breath, weakness, fatigue and confusion.
  2. Predominant hypoglycemia (low blood sugar) with symptoms that include rapid heartbeat, sudden changes in mood, shaking, sweating, nervousness, fatigue, paleness, headache, hunger and blurry vision.
  3. Mixed hyperglycemia and hypoglycemia, with symptoms of both conditions above.

Fortunately, with the availability of several different types of insulin (including long- and short-acting insulin and insulin pump therapy) that more precisely mimic the body’s normal insulin production, fluctuations in blood sugar levels are easier to manage. Still, some people do continue to experience brittle diabetes. Treatment may require interventions to assess the reason for the difficulty, to introduce behavioral changes to improve the dosing and monitoring of blood glucose, and to medically manage any adverse effects. It may be necessary to re-evaluate carbohydrate counting and insulin-matching techniques to be sure that needs are being met accurately. In some cases, brittle diabetes may be caused by psychiatric problems, such as Alzheimer’s disease, that prevent the proper matching of insulin needs to the body’s requirements.

Review the basics of diabetes and then brush up on your carbohydrate counting skills.