ONE of my patients — whom I will call Mrs. B — is a 78-year-old who has had Type 2 diabetes for over 30 years. She takes several injections of insulin each day. Her blood sugars have been running too high, but she doesn’t want to increase the dose of her insulin. She told me she simply can’t afford to. Insulin has been around for almost a century. The World Health Organization considers it an essential medicine, which means it should be available “at a price the individual and the community can afford.” So why is this product increasingly too expensive for many Americans? In the United States, just three pharmaceutical giants hold patents that allow them to manufacture insulin: Eli Lilly, Sanofi and Novo Nordisk. Put together, the “big three” made more than $12 billion in profits in 2014, with insulin accounting for a large portion.