Eli Lilly (LLY -0.13%) is a market darling, given its success in the GLP-1 weight-loss space. That's understandable, given the huge opportunity ahead in helping the world address a health issue that has such a material, and usually negative, impact on people's lives. But as you look at Eli Lilly, investors should consider these three things that are likely to matter more than you think.
1. Are Eli Lilly's GLP-1 drugs too successful?
Is there such a thing as too much success? That depends on how you look at it. In the second quarter of 2026, sales of Mounjaro rose 91% year over year. Sales of Zepbound jumped 46%. And the company's newly introduced Foundayo GLP-1 pill began generating revenue. Taken together, the weight-loss drugs produced nearly $15 billion of Eli Lilly's nearly $23 billion in revenue in the quarter. That's nearly two-thirds of the company's top line.
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That's a huge risk because Eli Lilly has all (OK, most) of its eggs in one single basket. Sure, that's been a very good thing so far, but eventually being so reliant on GLP-1 drugs is likely to be a problem.
2. Eli Lilly's GLP-1 growth is going to slow down (and it already is)
The next big thing that investors need to understand is simple math. As a business grows, future growth becomes increasingly difficult to achieve. So the success Eli Lilly is having right now, expanding its GLP-1 business, can't last forever. In fact, the growth slowdown may already be occurring. In the second quarter of 2025, Zepbound's sales grew 172% compared to the 46% in the second quarter of 2026. To be fair, Mounjaro's growth accelerated from 68% to 91%, so there's still room to run. But trees don't grow to the sky, as the old Wall Street saying goes.
3. Eli Lilly is using its GLP-1 success wisely
So Eli Lilly is seeing huge success in the GLP-1 space. That success won't last forever, given basic math, the highly competitive nature of the pharmaceutical industry, and the finite duration of drug patents. Which brings up another big opportunity and risk. Eli Lilly has been aggressively using its GLP-1 success to fund acquisitions that expand its business into new treatment areas.
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That's a wise move, so investors should be pleased with management. However, developing new treatments is time-consuming, difficult, and sometimes new drug candidates don't work out. So Eli Lilly is doing the right thing given the situation, but that doesn't mean it will result in long-term success for the business.
Three big-picture issues to watch at Eli Lilly
If you are looking at Eli Lilly today, three things to monitor are the sheer size of the GLP-1 business, its growth rate, and the company's efforts to expand beyond the weight-loss market. If you only see the success the company is achieving, you could end up surprised when the GLP-1 story eventually starts to look less positive.
