I had someone ask me which pen needles I use and if I use a new one with each injection, so here are my answers.
First, I use the BD Ultra-Fine Mini pen needle. They work well for me and are what my insurance will cover.
Second, Yes, I use a new pen needle with each injection that I take. Between split lantus doses and humalog injections for each meal, I use at least 5 pen needles a day. They are designed for single use, and reuse can lead to problems, such as the needle weakening and breaking off under the skin, inaccuracies in dosing, infections, pain, etc…
I know there are unfortunate circumstances where folks are forced to resort to reusing their needles. Whether it be due to the cost, running out while away from home, insurance denials, lack of education on use, etc… whatever the case, if possible always use a new needle each time. And make sure to properly dispose of it in a sharps container.