What is Hypoglycemia?


All people with diabetes, regardless of type or their method of treatment, suffer from high blood glucose levels (hyperglycemia) when left untreated.

The treatment of diabetes, whether pills or insulin, can lead to hypoglycemia.

Hypoglycemia is the term used to describe a low blood glucose level (BG). This would be a blood glucose level of less than 3.5 mmol/L (65 mg/dl)

Consequences of Hypoglycemia: A severe hypoglycemic event has a number of consequences. Some are well understood, others are surrounded by controversy.

Hypoglycemia can result in accident and injury. Other times it can be so severe it can be fatal. Repeated episodes of hypoglycemia appear to affect a person's ability to recognize the warning signs of approaching attacks in the future. Some researchers have even claimed to have found evidence that hypoglycemia may affect brain function.

Death: Some research estimates that between 4 and 13 percent of the deaths of people with type 1 diabetes are the result of hypoglycemic events.

"What's worrisome about these deaths is that they are due to the treatment," says Philip Cryer, MD, FACP past- president of the American Diabetes Association (ADA).

One especially frightening possibility for people on insulin that may be the result of severe hypoglycemia is what the journal Diabetic Medicine referred to in 1991 as "dead in bed syndrome." Victims of the syndrome are found dead in an undisturbed bed, observed to have been in good health the day before and are free from evidence of late diabetes complications.

Some of the strongest recent evidence in support of adverse effects of hypoglycemia on the brain comes from an article in the June 1997 issue of Diabetes Care. Using magnetic resonance imaging (MRI) researchers found that cortical (brain) atrophy was present in 45 percent of type 1 test subjects with a history of recurrent severe hypoglycemia. Cortical atrophy was nonexistent in type 1 subjects without such a history.

Regardless of the association between hypoglycemia and brain function, the researchers also found that these abnormal MRIs were far more prevalent in type 1s than in the nondiabetic population of comparable age (35 to 52 years old). The abnormalities discovered are normally associated with aging and are extremely rare in subjects of this age. The data suggest that they may "be a feature of diabetes and may represent accelerated brain aging associated with the metabolic disorder,".

It should be noted that very little is known about the consequences of hypoglycemia on children. Boyle points out that no subjects of the DCCT were under 14-years-old. Many researchers agree that the consequences of hypoglycemia could be much worse for children, however, because their brains are still developing.

Hypoglycemic Unawareness

A major disadvantage of repeated hypoglycemia is its effect on hypoglycemic awareness. A study from the journal Diabetes found that the enhanced rates of cerebral blood flow found at the onset of hypoglycemia are associated with a diminished perception of low blood glucose levels and weakening of the hormonal counter-regulatory response.

Generally, more severe hypoglycemic events equal more hypoglycemic unawareness. This can be remedied however.

According to Cryer, three separate studies have shown that hypoglycemic unawareness is "largely, if not entirely, the result of multiple hypoglycemic reactions." Two of these three studies also showed that as little as two to three weeks of "scrupulous avoidance of hypoglycemia will reverse hypoglycemic unawareness," says Cryer.

What Can Be Done?

A study by Bruce Bode, MD, published in 1996 in Diabetes Care suggests that pump therapy can greatly reduce the incidence of severe hypoglycemia. The study documents a more than six-fold decline in the incidence of severe hypoglycemia during the first year of pump therapy. The rate remained significantly lower in the three year follow up as well.

DCCT researcher Patrick Boyle, MD, mentions that two clinical studies have also shown that severe hypoglycemia can be reduced by more frequent BG testing.

"The majority of hypoglycemic events observed in the DCCT occurred at night. For that reason, patients should check their BG levels before bed and not go to sleep unless their BGs are in a good, safe range," adds Linda "Freddi" Fredrickson, MA, CDE, RN.