Optimal Insulin Delivery

Insulin therapy is only effective if it is delivered into the right tissue in the right way. Exogenous insulin is intended for the subcutaneous (SC) tissue, not the muscle or skin. If delivered into the latter, its absorption (pharmacokinetics (PK)) and action (pharmacodynamics (PD)) are unpredictable, which often leads to poor glucose control. Correct insulin therapy begins with matching the insulin to the site used. Typically, four sites are used for insulin injection or infusion: the abdomen lateral to the umbilicus all the way to the flanks, the anterior lateral upper half of the thigh, the deltoid region of the arm, and the upper outer quadrant of the buttocks. Regular insulin and neutral protamine Hagedorn (NPH) are both absorbed more rapidly from the arm and abdominal sites and more slowly from the thigh and buttocks. The newer insulin analogs, both rapid- and slow-acting, do not appear to be influenced by the site used for injection. In order to avoid intramuscular (IM) injections, patients should use the shortest needles currently available (the 4-mm pen needle and the 6-mm syringe needle). Very young children should raise a skin fold and inject into it even when using the 4-mm needle. Giving injections with the 6-mm needle at a 45° angle converts this needle into the equivalent of the 4 mm. Injection sites should be rigorously rotated, with the new injection being approximately 1 cm from previous injections. This measure helps prevent the most common complication of injection therapy, lipohypertrophy (LH). Injecting into LH leads to unstable PK and PD and deregulated glucose control, manifested as unexpected hypoglycemia, glycemic variability, and elevated HbA1c values. Comprehensive insulin deliver recommendations have recently been published