Intraregional differences in the absorption of unmodified insulin from the abdominal wall

Absorption of subcutaneously injected unmodified human 125I-insulin (5 U; 100 U ml-1) was studied concurrently from three areas of the abdominal wall (120 mm above, 120 mm lateral to, and 40 mm below the umbilicus), and one area of the thigh (upper midline), in nine Type 1 diabetic patients of normal body weight, and from deep (2 mm above muscle fascia) and superficial (3 mm beneath skin surface) sites in abdominal wall and thigh in 11 Type 1 diabetic patients. The absorption rates were followed continuously for 3 h with the patient in the supine position. Whereas 125I-insulin disappeared considerably faster from the site above the umbilicus than from sites below or lateral to the umbilicus or from the thigh (residual radioactivities after 175 min: 36 +/- 4 vs 49 +/- 5, 54 +/- 2, and 62 +/- 4 (+/- SE)%, respectively; p less than 0.05 or better), no significant differences were found between deep and superficial sites in either abdominal wall or thigh. The results suggest that insulin absorption rates from subcutaneous injection sites within the abdominal wall differ sufficiently for this to be of clinical importance.