Insulin may be injected into the subcutaneous tissues of the upper arms, front and side of the thighs, buttocks, and abdomen (except within 2 inches of the belly button). Intramuscular injections are not recommended for routine injections. Rotation of injection sites is important to prevent lipoatrophy or fat atrophy. Rotating within an area (e.g., rotating injections symmetrically across the abdomen) is recommended rather than rotating to a different area for each injection. This approach reduces inter-day variation in absorption. Differences in absorption between sites should be taken into account when selecting injection sites. Absorption is fastest in the abdomen, followed by the upper arms, thighs, and buttocks. Exercise increases absorption at the injection site, most likely due to increased blood flow to the skin and possibly due to local effects. Areas of fat gain often show lower absorption rates. The rate of absorption also differs subcutaneously and intramuscularly. The latter is absorbed more rapidly. Although intramuscular injections are not recommended as a routine method, they can be used in some cases (e.g., diabetic ketoacidosis or dehydration).