<SEC-DOCUMENT>0001022079-25-000187.txt : 20250725
<SEC-HEADER>0001022079-25-000187.hdr.sgml : 20250725
<ACCEPTANCE-DATETIME>20250725162800
ACCESSION NUMBER:		0001022079-25-000187
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250721
FILED AS OF DATE:		20250725
DATE AS OF CHANGE:		20250725

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KUPPUSAMY KARTHIK
		CENTRAL INDEX KEY:			0001955217
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-12215
		FILM NUMBER:		251151993

	MAIL ADDRESS:	
		STREET 1:		500 PLAZA DRIVE
		STREET 2:		C/O QUEST DIAGNOSTICS INC
		CITY:			SECAUCUS
		STATE:			NJ
		ZIP:			07094

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			QUEST DIAGNOSTICS INC
		CENTRAL INDEX KEY:			0001022079
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-MEDICAL LABORATORIES [8071]
		ORGANIZATION NAME:           	08 Industrial Applications and Services
		EIN:				161387862
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		500 PLAZA DRIVE
		CITY:			SECAUCUS
		STATE:			NJ
		ZIP:			07094
		BUSINESS PHONE:		9735202700

	MAIL ADDRESS:	
		STREET 1:		500 PLAZA DRIVE
		CITY:			SECAUCUS
		STATE:			NJ
		ZIP:			07094

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	CORNING CLINICAL LABORATORIES INC
		DATE OF NAME CHANGE:	19960903
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wk-form4_1753475272.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-07-21</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001022079</issuerCik>
        <issuerName>QUEST DIAGNOSTICS INC</issuerName>
        <issuerTradingSymbol>DGX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001955217</rptOwnerCik>
            <rptOwnerName>KUPPUSAMY KARTHIK</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>500 PLAZA DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>C/O QUEST DIAGNOSTICS INC</rptOwnerStreet2>
            <rptOwnerCity>SECAUCUS</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07094</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP, Clinical Solutions</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-07-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>L</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value>E</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>27</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>167.498</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10660</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>358</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1629</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>401(k)</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Reflects shares that were acquired pursuant to a dividend reinvestment plan administered by the reporting person's broker and eligible for deferred reporting on Form 5 under Rule 16a-6.  The reporting person has chosen to report such transaction early on this Form 4.</footnote>
        <footnote id="F2">The amount includes exempt purchases made under the Company's stock purchase plan since the date of the reporting person's last filing on Form 4.</footnote>
        <footnote id="F3">These underlying shares were acquired on a periodic basis by the trustee of the Company's tax qualified Profit Sharing (401(k)) Plan. The information was obtained from the plan administrator as of a current date. The number of shares is based on the account balance of the Company stock fund under the Plan (which includes some money market instruments) divided by the market price of the Company's stock as of that date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Sean D. Mersten, Attorney in Fact for Karthik Kuppusamy</signatureName>
        <signatureDate>2025-07-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
