Eli Lilly's (NYSE:LLY) mealtime insulin product Humalog brought in a whopping $2.4 billion last year. This drug comprises more than 10% of the drugmaker's total revenue, but Humalog's longevity could be compromised by an upcoming patent expiration, stiff competition by diabetes specialist Novo Nodisk (NYSE:NVO), and more competition in the future if MannKind (NASDAQ:MNKD) can get Afrezza, an ultra-rapid and inhalable insulin, on the market. In this video, health-care analyst Max Macaluso dives into this drug's sales, and breaks down the competitive landscape for investors.

Max Macaluso, Ph.D. has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.