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, and absorption of regular insulin (Actrapid) was delayed as determined by the clearance of 125 I-insulin. 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.