<SUBMISSION>
<ACCESSION-NUMBER>0000049071-08-000038
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20080331
<FILING-DATE>20080401
<DATE-OF-FILING-DATE-CHANGE>20080401
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>HUMANA INC
<CIK>0000049071
<ASSIGNED-SIC>6324
<IRS-NUMBER>610647538
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>500 W MAIN ST
<CITY>LOUISVILLE
<STATE>KY
<ZIP>40202
<PHONE>5025801000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>500 W. MAIN ST
<CITY>LOUISVILLE
<STATE>KY
<ZIP>40202
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>EXTENDICARE INC
<DATE-CHANGED>19740404
</FORMER-COMPANY>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>HERITAGE HOUSE OF AMERICA INC
<DATE-CHANGED>19671129
</FORMER-COMPANY>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>Dunbar Webster Roy
<CIK>0001305807
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-05975
<FILM-NUMBER>08730482
</FILING-VALUES>
<BUSINESS-ADDRESS>
<PHONE>972-605-5472
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>5400 LEGACY DRIVE
<CITY>PLANO
<STATE>TX
<ZIP>75024
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-03-31</periodOfReport>

    <issuer>
        <issuerCik>0000049071</issuerCik>
        <issuerName>HUMANA INC</issuerName>
        <issuerTradingSymbol>HUM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001305807</rptOwnerCik>
            <rptOwnerName>Dunbar Webster Roy</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>NETWORK SOLUTIONS, LLC</rptOwnerStreet1>
            <rptOwnerStreet2>13861 SUNRISE VALLEY DRIVE, SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>HERNDON</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>20171</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Humana Common</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9587</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Unit</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Humana Common</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1607</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5659</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Unit</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>45.63</value>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-03-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>479</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>45.63</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Humana Common</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>479</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>479</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Annual Director's fee payable in stock units, deferred at the election of the reporting person until his resignation of services as a director at which time the stock units will be payable in Humana Inc. common stock on a 1-for-1 basis, exempt pursuant to Rule 16(b)-3(d)(1).</footnote>
        <footnote id="F2">Director's cash fee elected to be converted into stock units, deferred at the election of the reporting person until his resignation of services as a director at which time the stock units will be payable in Humana Inc. common stock on a 1-for-1 basis, exempt pursuant to Rule 16(b)-3(d)(1).</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>W. Roy Dunbar</signatureName>
        <signatureDate>2008-04-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
