Interactive diabetes case 3: Hypoglycemia in a patient with type 1 diabetes – B2

ANSWER — Correct.

Initially, as the patient adjusted (reduced) his carbohydrate treatment of low glucose readings and/or symptoms of hypoglycemia, there was a marked reduction in the number of hyperglycemic values. Overtreatment of hypoglycemia is a common cause of hyperglycemia in insulin-treated patients.

Based on an estimated total insulin requirement of 44 units per day in this patient with type 1 diabetes but without obesity (estimated conservatively from a calculation of 0.6 units per kilogram of body weight per day), the dose of glargine insulin was almost one-half of the estimated total daily requirement and was not reduced further. However, the doses of lispro insulin were reduced as shown in the table (table 1).

This resulted in a marked reduction in the frequency of hypoglycemic events. Over several months, the hypoglycemia unawareness (a reversible phenomenon) resolved. The glycated hemoglobin (A1C) rose to 7.3 percent.

As the patient learned to count carbohydrates, his doses of lispro insulin were based on both the pre-meal glucose levels and the estimated carbohydrate content of the upcoming meal or snack using the so-called rule of 1500, which has two steps.

●Correction factor – First, the correction factor (used for correction of hyperglycemia) was calculated. The number 1500 was divided by the total insulin dose per 24 hours, ie, 1500/42 = 36 mg/dL (2 mmol/L), which represents the elevation of the blood glucose value above a reference point, such as 120 mg/dL (6.7 mmol/L), that would be covered ("corrected") by 1 unit of short-acting or very short-acting insulin.

●Prandial dose – Second, the prandial dose (insulin-to-carbohydrate ratio) was calculated. The correction factor (36 in this instance) was divided by 3; the result (12 in this case) is the number of grams of carbohydrate covered by 1 unit of insulin.

As an example, when the pre-meal blood glucose level is 204 mg/dL (11.3 mmol/L) and the meal is anticipated to have 60 grams of carbohydrate, the total lispro dose would be 7 units (2 units for correction of the hyperglycemia plus 5 units based on the insulin-to-carbohydrate ratio). This "rule" could more accurately be called the approximation of 1500. It provides a starting point for pre-meal and bedtime insulin doses, which should be modified based on the patient's own experience. The same is true of other rules and estimates for selecting insulin doses in type 1 diabetes.

Insulin reactions occurred only rarely, usually when the patient deviated from his diet. Most glucose values were in the target range of 80 to 130 mg/dL (4.4 to 7.2 mmol/L). Of course, some days were better than others. Over the next six months, the A1C fell to 6.9 percent.

In general, the prevention of hypoglycemia in diabetes involves addressing the issue in each patient contact and, if hypoglycemia is a problem, making adjustments in the regimen based on review and application of the principles of intensive glycemic therapy: diabetes self-management (supported by education and empowerment), frequent blood glucose monitoring, flexible and appropriate insulin or insulin secretagogue regimens, individualized glycemic goals, and ongoing professional guidance and support. Also, one must consider each of the known risk factors for hypoglycemia [1-5]. (See "Management of blood glucose in adults with type 1 diabetes mellitus" and "Hypoglycemia in adults with diabetes mellitus", section on 'Risk factors for hypoglycemia'.)

To explore the consequences of the other actions, return to the case at the beginning of this sequence. (See "Interactive diabetes case 3: Hypoglycemia in a patient with type 1 diabetes".)