<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-08-07</periodOfReport>
    <issuer>
        <issuerCik>0000049071</issuerCik>
        <issuerName>HUMANA INC</issuerName>
        <issuerTradingSymbol>HUM</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001112980</rptOwnerCik>
            <rptOwnerName>LORD JONATHAN T MD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>HUMANA INC.</rptOwnerStreet1>
            <rptOwnerStreet2>500 WEST MAIN STREET</rptOwnerStreet2>
            <rptOwnerCity>LOUISVILLE</rptOwnerCity>
            <rptOwnerState>KY</rptOwnerState>
            <rptOwnerZipCode>40202</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Sr VP &amp; Chief Innovation Off.</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Humana Common</value><footnoteId id="F1"/></securityTitle><transactionDate><value>2003-08-07</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>F</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>33769</value></transactionShares><transactionPricePerShare><value>16.16</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>66231</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeTransaction><nonDerivativeHolding><securityTitle><value>Humana Common</value><footnoteId id="F1"/></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1025</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>See Footnote</value><footnoteId id="F2"/></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable><derivativeHolding><securityTitle><value>Options</value><footnoteId id="F3"/></securityTitle><conversionOrExercisePrice><value>6.625</value></conversionOrExercisePrice><exerciseDate><footnoteId id="F4"/></exerciseDate><expirationDate><value>2010-05-18</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Humana Common</value><footnoteId id="F1"/></underlyingSecurityTitle><underlyingSecurityShares><value>110000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>110000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Options</value><footnoteId id="F3"/></securityTitle><conversionOrExercisePrice><value>12.995</value></conversionOrExercisePrice><exerciseDate><footnoteId id="F5"/></exerciseDate><expirationDate><value>2012-03-13</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Humana Common</value><footnoteId id="F1"/></underlyingSecurityTitle><underlyingSecurityShares><value>30000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>30000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Options</value><footnoteId id="F3"/></securityTitle><conversionOrExercisePrice><value>9.26</value></conversionOrExercisePrice><exerciseDate><footnoteId id="F6"/></exerciseDate><expirationDate><value>2013-03-13</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Humana Common</value><footnoteId id="F1"/></underlyingSecurityTitle><underlyingSecurityShares><value>50000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>50000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding></derivativeTable><footnotes><footnote id="F1">Each share of Common Stock contains a Right adopted on March 5, 1987, pursuant to the Company Rights Agreement, as amended and restated on February 14, 1996, and amended as of May 27, 1998 and March 1, 1999, which entitles holders of the Company's Common Stock, in the  event certain specified events occur, to acquire 1/100 of a share of Series A Participating Preferred Stock at a price of $145 per fractional share.</footnote><footnote id="F2">Shares held for the benefit of reporting person as of July 31, 2003 under the Humana Retirement &amp; Savings Plan including a routine disposition of shares to fund an administrative fee assessment under a Tax-Conditioned Plan, both exempt under Rule 16b-3(c).</footnote><footnote id="F3">Right to buy pursuant to the Company's 1996 Stock Incentive Plan for Employees.</footnote><footnote id="F4">Incentive and Non-Qualified stock options granted to reporting person on 5/18/00, NQ options vesting in two increments on 5/18/02 and 5/18/03, and ISO's vesting in three increments from 5/18/01 to 5/18/03.</footnote><footnote id="F5">Incentive and Non-Qualified stock options granted to reporting person on 3/13/02, NQ options vesting in three increments from 3/13/03 to 3/13/05, and ISO's vesting in two increments on 3/13/04 and 3/13/05.</footnote><footnote id="F6">Incentive and Non-Qualified stock options granted to reporting person on 3/13/03, NQ options vesting in three increments from 3/13/04 to 3/13/06, and ISO's vesting on 3/13/06.</footnote></footnotes><remarks/><ownerSignature><signatureName>Jonathan T. Lord, M.D.</signatureName><signatureDate>2003-08-08</signatureDate></ownerSignature></ownershipDocument>

