Insulin pens are premeasured to deliver insulin in increments ranging from one-half to 2 units with maximum dosage delivery amounts varying between manufacturers, according to Healthline. Diabetics use insulin pens to inject insulin in much the same way as with traditional insulin injection methods, without the need for premeasuring.
Insulin pens hold between 21 and 80 units of insulin and do not require continued refrigeration, notes Healthline. To use the pen, the diabetic prepares the injection site, attaches a needle to the pen, dials up the appropriate dose, and then injects the insulin. Pens may be refillable or disposable, depending on the brand and manufacturer.