<SEC-DOCUMENT>0001274737-22-000011.txt : 20220208
<SEC-HEADER>0001274737-22-000011.hdr.sgml : 20220208
<ACCEPTANCE-DATETIME>20220208162302
ACCESSION NUMBER:		0001274737-22-000011
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20220204
FILED AS OF DATE:		20220208
DATE AS OF CHANGE:		20220208

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Zack Debra
		CENTRAL INDEX KEY:			0001807743

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39049
		FILM NUMBER:		22601907

	MAIL ADDRESS:	
		STREET 1:		C/O EXAGEN, INC.
		STREET 2:		1261 LIBERTY WAY, SUITE C
		CITY:			VISTA
		STATE:			CA
		ZIP:			92081

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			EXAGEN INC.
		CENTRAL INDEX KEY:			0001274737
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-MEDICAL LABORATORIES [8071]
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1261 LIBERTY WAY
		CITY:			VISTA
		STATE:			CA
		ZIP:			92081
		BUSINESS PHONE:		(760) 560-1501

	MAIL ADDRESS:	
		STREET 1:		1261 LIBERTY WAY
		CITY:			VISTA
		STATE:			CA
		ZIP:			92081

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	EXAGEN DIAGNOSTICS INC
		DATE OF NAME CHANGE:	20031230
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_164435534136243.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2022-02-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001274737</issuerCik>
        <issuerName>EXAGEN INC.</issuerName>
        <issuerTradingSymbol>XGN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001807743</rptOwnerCik>
            <rptOwnerName>Zack Debra</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O EXAGEN INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1261 LIBERTY WAY</rptOwnerStreet2>
            <rptOwnerCity>VISTA</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92081</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Medical Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-02-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>50000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>87500</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents 50,000 restricted stock units. Each restricted stock unit represents a contingent right to receive one share of the Issuer's common stock. The restricted stock unit will vest with respect to 25% of the restricted stock units on each of the first, second, third and fourth anniversaries of February 4, 2022, subject to the Reporting Person's continued service through the applicable vesting date. In addition, the award may become fully vested upon a qualifying termination of employment in connection with a change in control.</footnote>
        <footnote id="F2">Represents 50,000 shares of restricted stock units granted on February 4, 2022 and 37,500 shares of restricted stock units granted on February 23, 2021.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Kamal Adawi, as attorney-in-fact</signatureName>
        <signatureDate>2022-02-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
