<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2014-12-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0000060714</issuerCik>
        <issuerName>LSB INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>LXU</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001005710</rptOwnerCik>
            <rptOwnerName>SBL, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>P O BOX 705</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>OKLAHOMA CITY</rptOwnerCity>
            <rptOwnerState>OK</rptOwnerState>
            <rptOwnerZipCode>73102</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-11-18</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1400</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1629954</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Series B Preferred</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <transactionCoding>
                <transactionFormType></transactionFormType>
            </transactionCoding>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>533333</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Series D Preferred</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F4"/>
            </conversionOrExercisePrice>
            <transactionCoding>
                <transactionFormType></transactionFormType>
            </transactionCoding>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F4"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>250000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1000000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">SBL, L.L.C. (&quot;SBL&quot;) is owned by Golsen Family, L.L.C. (&quot;GFLLC&quot;) (49%), Barry Golsen, a director and the president of the Issuer (17%), Steven Golsen, an executive officer of a subsidiary of the Issuer (17%), and Jack E. Golsen's daughter, Linda Rappaport (17%).  Golsen Petroleum Corporation (&quot;GPC&quot;) is a wholly owned subsidiary of SBL.  The amount shown in Table I includes 1,345,999 shares owned directly by SBL and 283,955 shares owned directly by GPC, and the amount shown in Table II includes 12,000 shares of the Issuer's Series B Preferred owned by SBL and 4,000 shares of the Issuer's Series B Preferred owned directly by GPC.  Voting and dispositive power over the securities held by SBL and GPC is possessed by Jack E. Golsen, who is the chief executive officer and chairman of the board of the Issuer, and Barry Golsen, a director and the president of the Issuer.</footnote>
        <footnote id="F2">GFLLC is owned by Jack E. Golsen, chief executive officer and chairman of the board of the Issuer, through his revocable trust (43.516%) and another trust (43.516%), his sons, Barry Golsen (4.323%), and Steven Golsen (4.323%), and his daughter, Linda Rappaport (4.323%).</footnote>
        <footnote id="F3">Each share of the Issuer's Series &quot;B&quot; 12% Cumulative Preferred Stock is convertible, at the option of the holder into 33.3333 shares of the Issuer's common stock.  Each share is convertible as long as such is outstanding.</footnote>
        <footnote id="F4">The Issuer's Series &quot;D&quot; 6% Cumulative, Convertible Class C Preferred Stock is convertible at the option of the holder into the Issuer's common stock at the rate of four shares of Preferred &quot;D&quot; for one share of common stock.  Each share is convertible as long as such is outstanding.</footnote>
        <footnote id="F5">Of these shares, 200,000 shares of the Issuer's common stock were pledged as collateral with a bank on March 5, 2012.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Jack E. Golsen, Manager</signatureName>
        <signatureDate>2015-01-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
