People living with diabetes who depend on insulin quickly learn which things truly matter — such as changing injection sites or correctly placing infusion sets. Of course, this assumes they are lucky enough to have a knowledgeable diabetologist.
The reason is not only to avoid scars or lipohypertrophy (a buildup of fatty tissue) that can interfere with insulin absorption. Different parts of the body absorb insulin at different rates, which can significantly affect its effectiveness.
Different Absorption Rates Depending on the Injection Site
Many studies have shown differences in insulin absorption depending on where it is injected. For example, insulin injected into the abdomen reaches its peak concentration faster than when it is injected into the thigh or upper arm. In the case of rapid-acting insulins, these differences are not always statistically significant, but they can still be clinically relevant for glucose regulation.
Application of These Findings in Automated Insulin Delivery (AID) Systems
In automated insulin delivery systems, variations in absorption across injection sites can significantly affect system performance — especially in those using machine learning algorithms. Such systems adjust insulin timing and action peaks based on the individual pharmacodynamics of each user. However, if the user changes the injection site, the system may not immediately recognize the difference, leading to less optimal glucose control.
Even systems without dynamic insulin-adjustment capabilities can face challenges, particularly when the user changes the infusion set location. In such cases, the system may automatically modify the user’s profile in an attempt to compensate for the changes.
Conclusion
Although research on this topic is still limited, understanding how insulin absorption varies by injection site can help improve the performance of automated insulin delivery systems. In practice, this means that switching the infusion site from the abdomen to the arm or leg can influence post-meal glucose levels and increase the risk of late-day hypoglycemia. Therefore, further studies and refinements of automated insulin systems could significantly enhance diabetes management — especially for patch pump users.
