Eli Lilly and Company vs Merck & Co., Inc.: Strategic Comparison

This in-depth comparison examines Eli Lilly and Company and Merck & Co., Inc. across revenue, market value, business model, competitive positioning, and long-term growth strategy. Whether you are researching Eli Lilly and Company on its own, evaluating Merck & Co., Inc., or weighing the two companies side by side, the breakdown below highlights where each company leads and where the gap between Eli Lilly and Company and Merck & Co., Inc. is widest.

On the headline numbers, Eli Lilly and Company reports annual revenue of $65.2B against $65.0B for Merck & Co., Inc., while their respective market capitalizations stand at $1.06T and $368.3B. Eli Lilly and Company is headquartered in United States and Merck & Co., Inc. operates from United States, and those different home markets shape how each company competes.

Eli Lilly and Company: Eli Lilly is a 150-year-old Indianapolis pharmaceutical company that has become the world's largest drugmaker by market value. For most of its history it was best known for insulin and Prozac. Since 2022, tirzepatide, a dual GIP/GLP-1 agonist sold as Mounjaro for type 2 diabetes and Zepbound for obesity, has transformed its scale, taking revenue from $28.5 billion in 2022 to $65.2 billion in 2025 and a guided $85-87 billion in 2026.

Merck & Co., Inc.: Merck & Co. is one of the largest U.S. pharmaceutical companies by sales, with $65.0 billion in 2025 revenue, about 75,000 employees and a market value near $368 billion in late September 2026. It researches, makes and sells cancer drugs, vaccines, cardiovascular and infectious-disease medicines, and animal health products in more than 140 markets. Keytruda, its PD-1 cancer immunotherapy, was the world's top-selling drug brand in 2025 and drives about half of company sales, so the company's current agenda centers on replacing that revenue before U.S. patent protection begins to lapse in 2028.

Eli Lilly and Company and Merck & Co., Inc. pursue distinct approaches to generating revenue, and understanding how each company operates is the foundation of any fair comparison between Eli Lilly and Company and Merck & Co., Inc..

Eli Lilly and Company business model: Lilly makes money by discovering, developing, manufacturing and selling patent-protected prescription medicines. Revenue comes mainly from product sales to wholesalers, pharmacies and health systems, with net prices set through negotiations with insurers, pharmacy benefit managers and governments; collaboration and royalty income adds a smaller share. Cardiometabolic medicines dominate: Mounjaro ($22.97 billion) and Zepbound ($13.54 billion) together produced about 56% of 2025 revenue. Lilly also sells directly to self-pay patients through LillyDirect, including Zepbound vials and Foundayo tablets, which reduces reliance on traditional pharmacy benefit channels for obesity care.

Merck & Co., Inc. business model: Merck makes money by selling patent-protected prescription medicines, vaccines and animal health products. The Pharmaceutical segment produced about $58.1 billion of 2025 sales, led by Keytruda/Keytruda Qlex ($31.7 billion), Gardasil ($5.2 billion), Januvia/Janumet ($2.5 billion) and Winrevair ($1.4 billion). Animal Health added about $6.4 billion from companion-animal products such as Bravecto and livestock vaccines. Sales go mainly to wholesalers, hospitals, governments and immunization programs, and the U.S. accounts for more than half of revenue. Merck reinvests heavily, spending $15.8 billion on R&D in 2025, and buys late-stage assets (Verona Pharma, Cidara, Terns) to replace revenue before patents expire.

The durability of a company's moat often decides long-term winners. Here is how the competitive advantages of Eli Lilly and Company stack up against those of Merck & Co., Inc..

Eli Lilly and Company competitive advantage: Lilly's advantage combines a century of diabetes and peptide-hormone expertise with manufacturing scale few rivals can match. Tirzepatide's dual GIP/GLP-1 mechanism produced greater weight loss than semaglutide in the head-to-head SURMOUNT-5 trial, and Foundayo gives Lilly a small-molecule GLP-1 pill that can be taken without food or water restrictions and is easier to mass-produce than peptides. Heavy investment in U.S. and European plants lets Lilly supply volume growth that competitors struggle to match.

Merck & Co., Inc. competitive advantage: Merck's edge rests on the scale of its Keytruda clinical program, with more than 40 approved indications, plus a large biologics manufacturing network and a vaccine franchise built over decades. Each new Keytruda approval reuses the same oncology sales relationships and safety data, which lowers the cost of every additional indication. The September 2025 approval of subcutaneous Keytruda Qlex, which sold $463 million in Q2 2026, gives Merck a newer formulation to move patients onto before IV biosimilars arrive. Animal Health adds a steadier, less patent-driven profit stream.

Future prospects matter as much as current results. The growth strategies below explain how Eli Lilly and Company and Merck & Co., Inc. each plan to expand from here.

Eli Lilly and Company growth strategy: Lilly's growth strategy has three parts: expand incretin supply and indications, add oral and next-generation obesity medicines, and diversify through oncology, immunology, neuroscience and genetic medicine. Foundayo (orforglipron) was approved by the FDA on April 1, 2026 and launched through LillyDirect, telehealth and U.S. retail pharmacies. Retatrutide, a GIP/GLP-1/glucagon triple agonist, is in Phase 3. Lilly continues to build U.S. and European manufacturing capacity and uses acquisitions to add pipeline assets.

Merck & Co., Inc. growth strategy: Merck's strategy is to use Keytruda cash flow to build a broader portfolio before 2028. It moved patients toward subcutaneous Keytruda Qlex (FDA-approved September 19, 2025), expanded Keytruda into earlier-stage cancers, and bought late-stage or commercial assets: Verona Pharma for about $10 billion (completed October 2025, adding COPD drug Ohtuvayre), Cidara Therapeutics for about $9.2 billion (completed January 2026, adding influenza preventive CD388), and Terns Pharmaceuticals for about $6.7 billion (completed in Q2 2026, adding CML candidate MK-4208). Earlier deals include Acceleron ($11.5 billion, 2021), Prometheus Biosciences ($10.8 billion, 2023) and the Daiichi Sankyo ADC collaboration (up to $22 billion, 2023).

A closer look at the financial trajectory of Eli Lilly and Company and Merck & Co., Inc. rounds out the comparison.

Eli Lilly and Company: Revenue rose from $28.5 billion in 2022 to $45.0 billion in 2024 and $65.2 billion in 2025, while net income nearly doubled to $20.6 billion. Growth accelerated again in 2026: second-quarter revenue rose 48% to $23.0 billion, with Mounjaro at $9.94 billion (up 91%) and Zepbound at $4.93 billion. Lilly raised 2026 revenue guidance to $85-87 billion and non-GAAP EPS guidance to $35.50-36.50. Capital expenditures reached $7.8 billion in 2025 as Lilly expanded production capacity.

Merck & Co., Inc.: Merck reported $65.0 billion in 2025 sales, up 1% from $64.2 billion in 2024, and $18.3 billion in net income attributable to Merck. Keytruda/Keytruda Qlex grew 7% to $31.7 billion, offsetting a 39% Gardasil decline. Momentum continued in 2026: Q2 2026 sales rose 5% to $16.6 billion, with Keytruda at $8.4 billion (including $463 million from Keytruda Qlex), Winrevair up 75% to $588 million and Animal Health up 8% to $1.8 billion. A $2.31-per-share charge for the Terns acquisition produced a Q2 GAAP net loss of $1.3 billion. In August 2026 Merck raised its full-year 2026 sales outlook to $66.3 billion to $67.3 billion, with non-GAAP EPS of $2.66 to $2.76 after Terns-related charges.