Priming your insulin pen lets you know that the pen is working properly before you inject your dose and it also makes sure that you are not injecting air as part of your dose. Air displaces some of the insulin and therefore you would not receive your total insulin allocation.
Why should insulin be at room temperature before it is injected?
Cold insulin can cause irritation at the injection site. To avoid any possible discomfort, insulin that has been refrigerated should be brought to room temperature before injection.
Why should syringes and pen needles not be reused?
Although the risk isn’t excessive, as insulin preparations contain antibacterial additives to inhibit growth of bacteria, reusing needles can still increase the possibility of a skin infection. This is especially true for people who do not practice good hygiene or have a pre-existing skin infection or a compromised immune system. In addition, every time a needle is reused is gets duller and is more apt to fragment or cause pain at the injection site.
However in practice, some patients find it economical to reuse needles. If needle reuse is planned, the needle must be recapped after each use. Patients should check carefully for signs of infection at the injection site and discuss needle reuse with their healthcare provider. Under no circumstances should needles be shared with others.