At the time, analysts had forecast 2013 earnings of $5.63 per share, on average.
The overhaul aims to cover millions of uninsured people and it will pay for that, in part, with a tax on premiums that starts in 2014. Hemsley has said that will start to affect UnitedHealth's performance next year because the insurer will have to account for it in the rates it charges.
Insurers set their prices based on the claims or expenses they expect to have in future.
Hemsley also has said the insurer will have to deal with tight government budgets that will squeeze its Medicare and Medicaid businesses.
Insurers offer privately run versions of the government's Medicare program for the elderly and disabled, and they also administer coverage of the state and federally funded Medicaid program, which provides coverage for the needy and disabled.
Conservative forecasts have become an investor day tradition for UnitedHealth, BMO Capital analyst Dave Shove said in a separate report. He noted, for instance, that the insurer initially forecast a drop in earnings for 2011, but actual earnings per share grew 15 percent that year.
UnitedHealth shares slipped 71 cents, or 1.3 percent, to $53.20 Monday afternoon while broader trading indexes fell less than 1 percent.