Quest Diagnostics Data Breach History

This page tracks the Quest Diagnostics data breach history and cybersecurity incidents affecting Quest Diagnostics (United States). BreachHistory currently indexes 5 publicly disclosed or catalogued incidents spanning 2012 through 2019, with approximately 32.0 million records reported as exposed across all indexed events. These totals may include overlapping datasets or third-party estimates and should not be interpreted as unique affected users.

The Quest Diagnostics breach timeline includes major data breaches, cyber attacks, data leaks, credential exposures, API abuse, and other security incidents. Each incident provides details on the estimated records exposed, attack method, affected data types, and supporting public sources. Currently, 0 incidents are company-confirmed.

Largest Quest Diagnostics Data Breaches

The largest indexed incidents include the 2019 — Quest Diagnostics: Poor security / misconfiguration, 20,000,000 records, the 2019 — Quest Diagnostics: One of the biggest blood testing providers in the…, and the 2016 — Quest Diagnostics: Quest Diagnostics regrets to notify you of a breach…, along with additional historical incidents involving exposed passwords, public databases, and large-scale data scraping. Record counts originating from threat actors or leak sites should be treated as estimates unless confirmed by Quest Diagnostics or a regulator. Below is the list of large data breaches:

• 2019 2019 — Quest Diagnostics: Poor security / misconfiguration, 20,000,000 records — about 20.0M records exposed · Catalogued incident
• 2019 2019 — Quest Diagnostics: One of the biggest blood testing providers in the… — about 11.9M records exposed · Catalogued incident
• 2016 2016 — Quest Diagnostics: Quest Diagnostics regrets to notify you of a breach… — about 34.0K records exposed · Catalogued incident
• 2016 2016 — Quest Diagnostics: Nov, 34K records — about 34.0K records exposed · Catalogued incident

What Information Was Exposed?

Depending on the incident, exposed data may include health and medical (PHI) records, and other personal information (PII). The exact data varies between incidents, so review each breach page before assuming your information was affected.

Quest Diagnostics Data Breach 2026

At the time of this update, no Quest Diagnostics data breach has been catalogued for 2026. New incidents are added as official disclosures, regulatory filings, or credible cybersecurity reports become available.

What To Do If You Were Affected

If you believe your account may have been involved in a Quest Diagnostics data breach, change any reused passwords, enable multi-factor authentication (MFA), monitor your account for suspicious activity, and be cautious of phishing emails or fake breach notifications.

This Quest Diagnostics breach history is maintained by BreachHistory using public disclosures, regulatory filings, security research, and clearly labelled third-party claims. For the complete breach timeline, records exposed, incident details, and AI Breach Risk Score, explore the sections on this page.