Currently, all types of insulin sold in the United States are packaged identically, either in 10cc vials or 1.5cc pen cartridges, with only the writing on the label to tell them apart. Insulin mixing has been standard practice for decades. The welfare of almost all insulin users depends on not confusing their Regular with their NPH, or their Lente, or their Ultralente, or their new, quick-acting Humalog. Not in a very safe place. Those of us who cannot reliably read insulin labels have been forced to depend on impermanent tactile cues like tape or rubber bands to tell one insulin from another, or else left to depend on sighted assistance.
Tape falls off, rubber bands break, and both can wind up on the wrong vial.
Sighted assistance is not always forthcoming. Diabetes is the leading cause of new blindness in the United States today. The Centers for Disease Control estimates diabetes costs 15,000 to 39,000 people their sight every year. This is not a small problem. The solution has been obvious from the start.