In a filing with the US Securities and Exchange Commission on Tuesday, LabCorp said that the breach occurred between August 1, 2018, and March 30, 2019.
Information that could have been postponed includes names, addresses, date of birth, and balance information .
Alerts are sent to LabCorp customers whose credit or bank account information may have been available.
The information comes one day after a collection company that worked with Quest Diagnostics informed the medical test company that the data of 11.9 million patients may have been affected by fractures.
The American Medical Collection Agency (AMCA), a supplier of billing collections, reported that "an unauthorized user had access to the AMCA system containing personal information, AMCA received from various entities, including from Quest."
Forensic experts are said to investigate breakup.