What is correct advice on injecting insulin?

The recommendation to have the needle remain in the skin for 10 seconds after injecting insulin is based on the goal of ensuring that the full dose of insulin is delivered into the subcutaneous tissue. When the needle is withdrawn immediately after the injection, some insulin may leak out of the injection site, leading to incomplete dosing. By leaving the needle in place for a brief period, it allows for better absorption and minimizes the risk of medication loss at the injection site. This practice helps ensure that patients achieve optimal glycemic control.

The other options do not align with best practices for insulin injection. For instance, immediate removal of the needle could compromise dosing, while injecting into the muscle can alter insulin absorption patterns, which is not advisable. Additionally, while the use of a new needle for each injection is important for preventing infection and ensuring the sharpness of the needle, the correct advice in this context specifically pertains to the timing of needle withdrawal after injection.