Andrew Witty has resigned as CEO of UnitedHealth Group, handing leadership to Stephen Hemsley due to personal reasons, with Witty remaining as senior adviser. The change follows a tumultuous period for the company, marked by a 15% drop in shares and heightened scrutiny over Medicare billing practices and rising medical costs. UnitedHealth has suspended its 2025 financial outlook, citing unexpectedly high expenses related to new Medicare Advantage beneficiaries. Despite these challenges, Hemsley aims to achieve long-term growth of 13-16% and has expressed commitment to improving health care amid ongoing public backlash following the murder of former executive Brian Thompson.