Just like there are two kinds of people, there are two kinds of pens. I think that both kinds of people are worth keeping, but that’s not true for pens.

Insulin pens are either prefilled and disposable or they are reusable. You throw away your prefilled pens when the insulin in it is finished. If you use a reusable pen, you just through away the insulin cartridge, but you better keep the pen.

Most people, however, would do better not to buy a reusable pen at all. That’s because insurance...