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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2011-06-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000736822</issuerCik>
        <issuerName>IMMUCOR INC</issuerName>
        <issuerTradingSymbol>blud</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001238960</rptOwnerCik>
            <rptOwnerName>LANCASTER RONNY B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ORASURE TECHNOLOGIES INC</rptOwnerStreet1>
            <rptOwnerStreet2>220 EAST FIRST STREET</rptOwnerStreet2>
            <rptOwnerCity>BETHLEHEM</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>18015</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Unit</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2011-06-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5542</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2012-06-09</value>
            </exerciseDate>
            <expirationDate>
                <value>2021-06-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5542</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5542</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each restricted stock unit represents a contingent right to receive one share of Issuer's common stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ronny Lancaster, by Rebecca Girod</signatureName>
        <signatureDate>2011-06-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0303
4
2011-06-09
0
0000736822
IMMUCOR INC
blud
0001238960
LANCASTER RONNY B
ORASURE TECHNOLOGIES INC
220 EAST FIRST STREET
BETHLEHEM
PA
18015
1
0
0
0
Restricted Stock Unit
2011-06-09
4
A
0
5542
0
A
2012-06-09
2021-06-09
Common Stock
5542
5542
D
Each restricted stock unit represents a contingent right to receive one share of Issuer's common stock.
Ronny Lancaster, by Rebecca Girod
2011-06-13