When it comes to injecting insulin, the stomach, the buttocks, the back of the arm and the thigh have something in common. They usually contain enough fatty issue to be good depots for insulin administration. As any educator will tell you, insulin should be injected into fat.
If injected directly into muscle, aside from being painful, it will be absorbed much too rapidly. The insulin may reach your blood stream before your digestive system has the time to release glucose from the food you eat. (There are other areas on the body, for example, the breasts, which have adequate fatty tissue but have not been sufficiently studied to determine their absorption rates.)
Each of these approved areas absorbs insulin at a slightly different rate, and knowing this can help you make the best decision about where to inject depending on your blood glucose. In general, insulin is more quickly absorbed from the stomach followed by the arm, the thigh, and the buttocks.
For example if your blood glucose is low before a meal, you may want to inject into the buttock area because insulin is absorbed most slowly here. On the other hand, if you are hyperglycemic the stomach may be the best choice as it has the fastest absorption rate. This variability is most prominent with NPH and regular insulin and not as much a factor with the rapid acting insulins.
Rotate your sites
Injecting insulin into the same site over and over again can lead to the fat below the skin becoming hard and lumpy. Aside from being unsightly, it can change the way your insulin is absorbed so you won’t easily know when the insulin will start working or peak.
Tips for Injecting Insulin
Stay at least two inches away from the belly button, or any scars or moles.
Inject at least 4 inches (or approximately one hand-width) above the knee and at least 4 inches down from the top of the leg. The best area on the leg is the top and outer area of the thigh.
Inject into the fatty tissue in the back (not the side) of the arm between the shoulder and the elbow.
Inject into the hip or “wallet area” and not into the lower buttock area.
A few additional points
- To make sure that your insulin is absorbed consistently, it may be best to give all injections in one or two areas of the body and rotate where you inject the insulin within that site for a period of time.
- Use a different site for each time of day. For example, inject your morning insulin in your stomach and your evening insulin in your thigh. Be sure to rotate within the site.
- Physical activity may increase insulin absorption. It’s best not to inject in your arm or thigh if you have just exercised or plan to exercise (your arms would absorb insulin quickly if you were doing a set of bicep curls, for instance). So your stomach may be the best site choice if you will be physically active.
- Hot temperatures tend to increase insulin absorption, while cold temperatures can decrease absorption. Be careful about injecting insulin after taking a hot shower, a bath or being out in the cold.
- Smoking may decrease insulin absorption, which is another good reason to quit!