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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-08-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001438133</issuerCik>
        <issuerName>TANDEM DIABETES CARE INC</issuerName>
        <issuerTradingSymbol>TNDM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001582779</rptOwnerCik>
            <rptOwnerName>Allen Dick</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TANDEM DIABETES CARE, INC.,</rptOwnerStreet1>
            <rptOwnerStreet2>11075 ROSELLE STREET</rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92121</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-08-27</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>69.19</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>37000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The shares were given as a bona fide gift to Orange County Community Foundation (OCCF).</footnote>
        <footnote id="F2">The securities are held by the Allen Family Trust dated October 12, 1981.</footnote>
        <footnote id="F3">The securities are held by the Gammon Children's 2000 Trust FBO Hannah Lee Gammon. The Reporting Person is co-trustee of the Gammon Children's 2000 Trust FBO Hannah Lee Gammon and has shared voting and investment power over the securities held by the Gammon Children's 2000 Trust FBO Hannah Lee Gammon and may be deemed to have indirect beneficial ownership of such securities. The Reporting Person disclaims beneficial ownership of such securities held by the Gammon Children's 2000 Trust FBO Hannah Lee Gammon.</footnote>
        <footnote id="F4">The securities are held by the Gammon Children's 2000 Trust FBO Jake Allen Gammon. The Reporting Person is co-trustee of the Gammon Children's 2000 Trust FBO Jake Allen Gammon and has shared voting and investment power over the securities held by the Gammon Children's 2000 Trust FBO Jake Allen Gammon and may be deemed to have indirect beneficial ownership of such securities. The Reporting Person disclaims beneficial ownership of such securities held by the Gammon Children's 2000 Trust FBO Jake Allen Gammon.</footnote>
        <footnote id="F5">The securities are held by Allen Cornerstone Ventures L.P. The Reporting Person is the managing partner of Allen Cornerstone Ventures L.P. and may be deemed to have indirect beneficial ownership of such securities. The Reporting Person disclaims beneficial ownership of such securities held by Allen Cornerstone Ventures L.P., except to the extent of his proportionate pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>s/ David B. Berger, Attorney-in-Fact for Dick P. Allen</signatureName>
        <signatureDate>2019-08-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
