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

    <schemaVersion>X0305</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-04-17</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000101295</issuerCik>
        <issuerName>UNITED GUARDIAN INC</issuerName>
        <issuerTradingSymbol>UG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000943504</rptOwnerCik>
            <rptOwnerName>GLOBUS KENNETH H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O UNITED-GUARDIAN, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>230 MARCUS BLVD., P.O. BOX 18050</rptOwnerStreet2>
            <rptOwnerCity>HAUPPAUGE</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>11788</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-04-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>77000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1478293</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>SEE FOOTNOTE</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-04-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>77000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1401293</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>SEE FOOTNOTE</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">569,293 shares held directly and 909,000 owned beneficially</footnote>
        <footnote id="F2">Transfer to the beneficiary of stock held in trust.  No sale of stock involved.</footnote>
        <footnote id="F3">569,293 shares held directly; 760,000 shares held indirectly as joint trustee (sole voting trustee) of the Alfred R. Globus Testamentary Trust; 77,000 shares held indirectly as trustee of daughter's trust; 72,000 shares owned by wife</footnote>
        <footnote id="F4">569,293 shares held directly and 832,000 owned beneficially</footnote>
        <footnote id="F5">569,293 shares held directly; 760,000 shares held indirectly as joint trustee (sole voting trustee) of the Alfred R. Globus Testamentary Trust; 72,000 shares owned by wife</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Kenneth H. Globus</signatureName>
        <signatureDate>2012-04-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0305
4
2012-04-17
0
0000101295
UNITED GUARDIAN INC
UG
0000943504
GLOBUS KENNETH H
C/O UNITED-GUARDIAN, INC.
230 MARCUS BLVD., P.O. BOX 18050
HAUPPAUGE
NY
11788
1
1
1
0
President
Common Stock
2012-04-17
4
J
0
77000
0
D
1478293
I
SEE FOOTNOTE
Common Stock
2012-04-17
4
J
0
77000
0
D
1401293
I
SEE FOOTNOTE
569,293 shares held directly and 909,000 owned beneficially
Transfer to the beneficiary of stock held in trust.  No sale of stock involved.
569,293 shares held directly; 760,000 shares held indirectly as joint trustee (sole voting trustee) of the Alfred R. Globus Testamentary Trust; 77,000 shares held indirectly as trustee of daughter's trust; 72,000 shares owned by wife
569,293 shares held directly and 832,000 owned beneficially
569,293 shares held directly; 760,000 shares held indirectly as joint trustee (sole voting trustee) of the Alfred R. Globus Testamentary Trust; 72,000 shares owned by wife
Kenneth H. Globus
2012-04-18