Key Points
Berkshire Hathaway's market cap is roughly the same as Eli Lilly's, at about $1.1 trillion.
GLP-1 weight-loss drugs account for around two-thirds of Eli Lilly's top line.
Weight loss is a huge market, but patent expirations will eventually create revenue headwinds.
Warren Buffett is no longer involved in running Berkshire Hathaway (NYSE: BRKA)(NYSE: BRKB), but the company he built is nothing short of impressive. With a roughly $1.1 trillion market cap as of this writing, it is a diversified giant with businesses spread across insurance, utilities, transportation, energy, retail, and manufacturing. And that doesn't even do justice to the company's scale.
So how does a company with just one big product compare? That's the real question investors need to ask when they look at Eli Lilly's (NYSE: LLY) roughly $1.1 trillion market cap. The answer isn't as clear-cut as it may seem when you consider what Eli Lilly is doing with the profits from its highly successful GLP-1 weight-loss drugs. Here's what you need to know.
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Berkshire Hathaway vs Eli Lilly? No comparison.
Warren Buffett built Berkshire Hathaway using his simple but highly effective investment approach. To sum it up, Buffett liked to buy well-run companies when they were attractively priced and then hold them for the long term. That allowed him to benefit from the businesses' growth over time, though he generally took a hands-off approach to day-to-day operations. Buffett let company managers do their job while he focused on continuing to build Berkshire Hathaway's portfolio of owned businesses.
The end result is that Buffett handed off a massively diversified company to his hand-picked successor, Greg Abel. If one business within Berkshire Hathaway were to falter, it wouldn't be a particularly big deal. In fact, Greg Abel used headwinds in the housing sector to augment the company's housing-related businesses when he bought Taylor Morrison Home in early 2026.
This is very different from Eli Lilly. The giant pharmaceutical company has achieved huge success in the emerging GLP-1 weight-loss niche. But its GLP-1 product lineup, which includes shots and pills, accounted for nearly two-thirds of the company's revenues in the first half of 2026. That makes the company look like a one-trick pony in comparison to Berkshire Hathaway.
Eli Lilly has a GLP-1 problem, and it's working on it
The problem isn't just the size of the company's GLP-1 revenues. The deeper issue is that drugs have limited patent protections. And once those patent protections end, generic versions of the drug can be sold. That normally results in material revenue declines in the branded drugs. There's some time to go before Eli Lilly has to worry about its GLP-1 drugs facing generic competition, but that competition will eventually come. That's just how the drug sector works.
Which is why it is so important that Eli Lilly is using its GLP-1 profits to expand its healthcare business in new directions. To put it simply, Eli Lilly has gone on a GLP-1-fueled acquisition spree, buying its way into new treatment niches that greatly improve its diversification. To be fair, many of the acquisitions involve drugs that are still in development, so some of this spending may prove to have been in vain. However, Eli Lilly's drug pipeline is robust and diversified, creating a stronger foundation than the huge dependence on GLP-1 revenue may suggest.
Can Eli Lilly's rally keep going?
Eli Lilly's stock has risen over 50% in a year, as of this writing. It is up 400% over the past five years. That incredible run is largely driven by the company's GLP-1 success, which has investors very excited about Eli Lilly. The stock's price-to-earnings ratio is 43x, which is well above the industry average of 27x. Eli Lilly looks expensive, relatively speaking.
When you bring it all together, Eli Lilly is working to diversify its business (at least moving it in the general direction of Berkshire Hathaway). But a lot is riding on the acquisitions it is making, and the GLP-1 patent clock is ticking. If you have a big gain in Eli Lilly, it might make sense to take some profits even if you don't sell your entire position. If you are thinking about buying the stock today, the rally could be more tenuous than you think, given Eli Lilly's huge exposure to just one category of drugs and the still unproven success of its acquisition program.
Reuben Gregg Brewer has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Berkshire Hathaway and Eli Lilly. The Motley Fool has a disclosure policy.