Medicare Advantage's two giants are trading places

KFF refreshed its annual Medicare Advantage enrollment brief on July 1 with March 2026 data, and the steady headline number hides a real shakeup underneath. More than half of eligible Medicare beneficiaries, 55 percent, or 35.2 million of 64.2 million people with both Part A and Part B, are now enrolled in Medicare Advantage. Overall growth continued to slow, adding about 1.1 million people, a 3 percent increase. The movement is inside the total. UnitedHealth Group, long the largest Advantage insurer, saw its share fall from 29 percent to 26 percent, losing nearly 647,000 enrollees between March 2025 and March 2026. Humana went the other way, growing from 17 percent to 20 percent of the market with 1.3 million new enrollees, the largest gain of any insurer. Together the two still cover 46 percent of everyone in Medicare Advantage, the same as last year, but the gap between first and second place narrowed sharply. Some smaller insurers grew fast too: Devoted Health added about 258,000 members and SCAN Group about 136,000, while Elevance lost 346,000. None of this is an accident. UnitedHealthcare has told investors it is prioritizing profit margins over membership, trimming the counties and plans it offers, while Humana priced its plans to grow. For a person on one of these plans, strategy is not an abstraction: it shows up as county exits, benefit changes, and network shifts at renewal time. A shrinking insurer is not automatically worse and a growing one is not automatically better; both postures can change what your specific plan looks like next year. The practical takeaway is the same either way: when the Annual Notice of Change arrives in September, read it, and compare your plan against the market during fall enrollment rather than assuming next year looks like this year.