The systematic switching of insulin injections from one site to another. For years, doctors have emphasized the need for people with diabetes to rotate their injection sites rather than injecting into the same place each time. Injecting into the same spot can cause lipohypertrophy, the buildup of fat under the skin, which can slow the absorption of insulin, or lipoatrophy, the wasting of fat under the skin, which can be unsightly. (Lipoatrophy is less likely to occur in people using only human insulin.)
The best places to inject insulin are the upper arms, the thighs, the buttocks, and the abdomen (at least two inches away from the navel). Because the rates of absorption vary considerably from one body region to another, the American Diabetes Association (ADA) currently recommends rotating injection sites within body regions rather than rotating to a different region with each injection.
Insulin is absorbed fastest from the abdomen, followed by the arms, the thighs, and the buttocks. (However, exercising an arm or leg after an injection can increase blood flow and speed insulin absorption from those areas.) The ADA recommends taking this variability into account when choosing injection sites. Everyone absorbs insulin somewhat differently, so the best way to find out what effect a given injection site is having is to monitor your blood glucose levels. Paying close attention to how you rotate your injection sites can help to eliminate high and low swings in blood glucose level.