BACKGROUND: Insertion of an insulin catheter for continuous subcutaneous insulin infusion into the subcutaneous adipose tissue (SAT) causes a tissue trauma that may have consequences for insulin absorption. We evaluated the importance of insulin catheter wear-time on subcutaneous adipose tissue blood flow (ATBF) and absorption of the rapid-acting insulin analog insulin aspart over a period of 4 days. METHODS: Teflon insulin catheters (Medtronic, Minneapolis, MN) were inserted into the abdominal SAT of 10 healthy men without diabetes (mean +/- SEM age, 23.0 +/- 1.1 years; body mass index, 22.1 +/- 0.7 kg/m(2)) and connected to an insulin pump delivering a constant rate of isotonic saline for 4 days. Subjects participated in four study days (days 0, 1, 2, and 4) during which ATBF around the catheter tip was measured by (133)Xe clearance and absorption of an insulin aspart bolus (0.1 U/kg) was measured for 4 h. RESULTS: ATBF increased from day 0 to day 2 after catheter insertion (2.6 +/- 0.6 to 4.5 +/- 0.8 mL/100 g/min; P = 0.030). By day 4, ATBF had returned to day 0 level. Time to peak plasma insulin aspart concentration after bolus administration decreased with catheter wear-time from 55 +/- 3 min on day 0 to 45 +/- 4 min on day 4 (P = 0.019). Neither peak plasma concentration nor area under the curve of insulin aspart changed significantly. CONCLUSIONS: Insertion of a Teflon insulin catheter into the SAT results in increased ATBF and faster absorption of insulin aspart in a period of 4 days without any change in the total amount of insulin aspart absorbed.