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

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-02-17</periodOfReport>

    <issuer>
        <issuerCik>0000722104</issuerCik>
        <issuerName>SAVIENT PHARMACEUTICALS INC</issuerName>
        <issuerTradingSymbol>SVNT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001218810</rptOwnerCik>
            <rptOwnerName>KANNER DOV</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BIO-TECHNOLOGY GENERAL (ISRAEL) LTD.</rptOwnerStreet1>
            <rptOwnerStreet2>KIRYAT WEIZMANN</rptOwnerStreet2>
            <rptOwnerCity>REHOVOT, ISRAEL</rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode>76326</rptOwnerZipCode>
            <rptOwnerStateDescription>ISRAEL</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Options to purchase Common Stock, $.01 par value per share</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.31</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-02-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>85000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4.31</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-02-17</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $.01 par value per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>85000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>564005</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">These options will become exercisable as to 21250 shares on each of 2/17/05, 2/17/06, 2/17/07 and 2/17/08, provided that Mr. Kanner is employed by the Company on these dates.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Beata Smith as attorney-in-fact for Dov Kanner</signatureName>
        <signatureDate>2004-02-19</signatureDate>
    </ownerSignature>
</ownershipDocument>

