Impaired Absorption of Insulin Aspart From Lipohypertrophic Injection Sites

• AUC, area under the curve

Lipohypertrophy is a common side effect of subcutaneous insulin therapy, occurring in up to 50% of patients with type 1 diabetes (1–3). It is generally held that absorption of insulin from such palpably abnormal sites is erratic, although the consequence thereof on glucose control has been considered controversial (1,4,5). Notably, a recent study using the continuous glucose monitoring system to monitor swings of blood glucose documented a significant correlation between the mean of daily differences of glucose and the severity of injection site lipohypertrophy (6). Few studies have investigated insulin uptake from lipohypertrophic tissue. Absorption of isophane (NPH) insulin, as determined by plasma free insulin, was found to be markedly defective at abnormal injection sites (7), and absorption of regular insulin (Actrapid) was delayed as determined by the clearance of ¹²⁵I-insulin (8). It was concluded from these studies that the differences were of sufficient magnitude to be of clinical importance. Currently, both of these insulin preparations give way to insulin analogs. Therefore, the present study was conducted to investigate whether the absorption of a single subcutaneous dose of insulin aspart is impaired when administered to lipohypertrophic tissue in patients with type 1 diabetes.