CVS Health is one of the largest health companies in the U.S., operating across three interconnected businesses: Aetna (health insurance), Caremark (pharmacy benefits management or PBM), and CVS Pharmacy (retail pharmacy). Aetna insures roughly 26-27 million members across Medicare Advantage, Medicaid, and commercial plans, collecting fixed premiums from employers, individuals, and government programs and earning a margin when premiums exceed medical costs. Caremark manages prescription drug benefits for about 87-90 million plan members, negotiating drug prices and rebates with manufacturers, managing formularies, and running mail order and specialty pharmacy operations. CVS Pharmacy operates roughly 9,000 retail locations and dispenses about 1.8 billion prescriptions annually, representing approximately 28-29% of all U.S. retail pharmacy scripts. CVS argues that combining these three businesses under one roof lowers costs and improves outcomes — for example, Caremark's formulary tools lower drug costs for Aetna members, and Aetna members who use CVS Pharmacy show higher medication adherence. Beyond the core three, CVS owns Oak Street Health (246 primary care centers serving Medicare patients on a value-based model) and Signify Health (in-home health evaluations). CVS has been transitioning Caremark to a rebate pass-through model ("TrueCost") and its retail pharmacy to a cost-plus reimbursement model ("CostVantage"), both designed to create more transparent and durable margin structures. Near-term focus is on balance sheet repair and recovering Aetna's Medicare Advantage margins, which deteriorated sharply in 2024 due to higher-than-expected medical utilization.