-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0001140361-10-034162.txt : 20100817
<SEC-HEADER>0001140361-10-034162.hdr.sgml : 20100817
<ACCEPTANCE-DATETIME>20100817182107
ACCESSION NUMBER:		0001140361-10-034162
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100813
FILED AS OF DATE:		20100817
DATE AS OF CHANGE:		20100817

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Spinell Gary Michael
		CENTRAL INDEX KEY:			0001485591

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-24657
		FILM NUMBER:		101024191

	MAIL ADDRESS:	
		STREET 1:		600 S. ROYAL LANE
		STREET 2:		SUITE 200
		CITY:			COPPELL
		STATE:			TX
		ZIP:			75019

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MANNATECH INC
		CENTRAL INDEX KEY:			0001056358
		STANDARD INDUSTRIAL CLASSIFICATION:	MEDICINAL CHEMICALS & BOTANICAL PRODUCTS [2833]
		IRS NUMBER:				752508900
		STATE OF INCORPORATION:			TX
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		600 SOUTH ROYAL LANE
		STREET 2:		SUITE 200
		CITY:			COPPELL
		STATE:			TX
		ZIP:			75019
		BUSINESS PHONE:		9724717400

	MAIL ADDRESS:	
		STREET 1:		600 SOUTH ROYAL LANE
		STREET 2:		SUITE 200
		CITY:			COPPELL
		STATE:			TX
		ZIP:			75019
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-08-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001056358</issuerCik>
        <issuerName>MANNATECH INC</issuerName>
        <issuerTradingSymbol>MTEX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001485591</rptOwnerCik>
            <rptOwnerName>Spinell Gary Michael</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>600 S ROYAL LN #200</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>COPPELL</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr VP Finance &amp; Admin</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Right to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.21</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2010-08-13</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2016-06-11</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, Par Value $0.0001 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Right to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>7.31</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2010-08-13</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2017-09-05</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, Par Value $0.0001 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>11000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Right to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.46</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2010-08-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10190</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <value>2020-08-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, Par Value $0.0001 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10190</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21190</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The option provided for vesting in three equal annual installments beginning June 12, 2007.</footnote>
        <footnote id="F2">The option provided for vesting in three equal annual installments beginning September 6, 2008.</footnote>
        <footnote id="F3">On August 16, 2010, the issuer canceled, pursuant to the issuer's option exchange program, an option for 20,000 shares of Mannatech common stock granted to the reporting person on June 12, 2006.  In exchange, the reporting person received a replacement option, for 8,470 shares, having an exercise price of $2.46 a share.</footnote>
        <footnote id="F4">On August 16, 2010, the issuer canceled, pursuant to the issuer's option exchange program, an option for 3,000 shares of Mannatech common stock granted to the reporting person on September 6, 2007.  In exchange, the reporting person received a replacement option, for 1,720 shares, having an exercise price of $2.46 a share.</footnote>
        <footnote id="F5">The option vests in three equal annual installments beginning August 16, 2011.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Stephen D. Fenstermacher, Co-CEO and CFO, by Power of Attorney</signatureName>
        <signatureDate>2010-08-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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