Original Iletin--1923. This was made of beef and was Regular/neutral insulin. The 2 vial cartons illustrate the strengths insulin came in at the time; the carton on the left is U20 strength while the one on the right is U40.
Studies done on all Lilly vialed insulins--Humulin, Iletin, and Humalog, show that the stoppers have sufficient resealing properties to maintain a good seal after 100 punctures. What this means to you is that the insulin will stay potent longer[2].
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