[12] In July 2013, the People's Republic of China announced that they were investigating allegations of fraud perpetrated by GSK going back to 2007 and involving billions of Chinese renminbi.

[13] Witty stated "It appears that certain senior executives in the China business have acted outside our processes and controls to both defraud the company and the Chinese health care system.

"[14] From 2013 to 2015, Witty was on the UNAIDS–Lancet Commission for Defeating AIDS and Advancing Global Health, co-chaired by Joyce Banda, Nkosazana Dlamini Zuma and Peter Piot.

[27] In April 2021, he was also appointed to the Pandemic Preparedness Partnership (PPP), an expert group chaired by Vallance to advise the G7 presidency held by the government of Prime Minister Boris Johnson.

[29][30] On 15 May 2024, a class action lawsuit was brought by the City of Hollywood Firefighters' Pension Fund alleging that Witty and two other UnitedHealth Group executives were involved in insider trading in 2023.

The suit alleges that in addition to Witty, Brian Thompson and Stephen Hemsley sold a combined total of $120 million of UHC stock four months before shareholders and the general public were informed that the company was being investigated by the United States Department of Justice in regard to an antitrust suit involving Optum's potential buyout of Change Healthcare.

[31] On 6 December 2024, after the murder of former CEO of UnitedHealth Group's subsidiary company UnitedHealthcare, Brian Thompson,[32] a video was leaked in which Witty stated, "Our role is a critical role, and we make sure that care is safe, appropriate, and is delivered when people need it" and that the insurer will continue to prevent "unnecessary care" and advised that people refrain from discussing anything with the media.