Test Your Knowledge Answer #418

The dawn phenomenon is defined as an increase in blood glucose levels during the early morning hours (4 AM to 8 AM). This phenomenon occurs more often in type 1 diabetes than in type 2 diabetes. Conventional insulin regimens rarely correct the dawn phenomenon without precipitating nocturnal hypoglycemia. Although a basal-bolus regimen using insulin glargine offers increased lifestyle flexibility, correction of fasting hyperglycemia is very difficult without causing hyperinsulinemia and increasing the hypoglycemia risk at other times during the day, as occurred in this patient. Therefore, the ability to adjust the basal infusion rate to match physiologic insulin requirements gives continuous subcutaneous insulin infusion therapy a clear advantage over multiple daily injection regimens in patients who experience the dawn phenomenon. Any patient who may be a candidate for continuous subcutaneous insulin infusion therapy should be referred to an endocrinologist who is experienced in this method of insulin delivery.

 

Decreasing the insulin glargine dosage could decrease the risk for hypoglycemia but would not control fasting blood glucose levels. This patient's hypoglycemia was likely caused by too much insulin glargine, not too much insulin lispro. The fact that he can reduce or omit lispro at meals without causing hyperglycemia by the next meal is further evidence that the glargine dosage is excessive. Administering glargine in the morning might reduce the risk for nocturnal hypoglycemia but would probably not eliminate the dawn phenomenon and could possibly worsen fasting hyperglycemia because of the waning of the previously administered glargine. The patient's current dosage of glargine has corrected the dawn phenomenon at the expense of increased hypoglycemia. In general, lowering the insulin-to-carbohydrate ratio can help reduce post-meal hypoglycemia. However, in this case, the patient's hypoglycemia is clearly caused by an excessively large dosage of glargine. This is supported by the fact that his episode of severe hypoglycemia occurred when he had not taken any fast-acting insulin. Also, he experiences almost daily hypoglycemia, especially if he skips breakfast (presumably skipping lispro as well). 

 

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