Exhibit 23

Consent of Independent Registered Public Accounting Firm

We have issued our report dated June 29, 2020, with respect to the financial statements and supplemental information included in the Annual Report of The Profit Sharing Plan of Quest Diagnostics Incorporated on Form 11-K for the year ended December 31, 2019. We consent to the incorporation by reference of said report in the Registration Statement of Quest Diagnostics Incorporated on Form S-8 (File No. 333-157447).

/s/ Grant Thornton LLP

Boston, Massachusetts

June 29, 2020