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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2007-08-07</periodOfReport>

    <dateOfOriginalSubmission>2007-08-09</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001287865</issuerCik>
        <issuerName>MEDICAL PROPERTIES TRUST INC</issuerName>
        <issuerTradingSymbol>MPW</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001331608</rptOwnerCik>
            <rptOwnerName>Aldag Edward K JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1000 URBAN CENTER DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 501</rptOwnerStreet2>
            <rptOwnerCity>BIRMINGHAM</rptOwnerCity>
            <rptOwnerState>AL</rptOwnerState>
            <rptOwnerZipCode>35242</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman, President &amp; CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value, $.001</value>
            </securityTitle>
            <transactionDate>
                <value>2007-08-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>150000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1019022</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $.001</value>
            </securityTitle>
            <transactionDate>
                <value>2007-08-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>250000</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1019022</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares of restricted stock awarded pursuant to the Company's Second Amended and Restated 2004 Equity Incentive Plan and which vest ratably on December 31 of each year over a seven year period beginning December 31, 2007.</footnote>
        <footnote id="F2">Represents shares of restricted stock awarded as core performance awards (CPRE).  CPRE vest annually and ratably over a 7 year period (beginning 3/1/07 through 12/31/13) contingent on the Company acheiving a simple 9% annual total return to shareholders (pro-rated to 7.5% for the first vesting period from 3/1/07 to 12/31/07). CPRE are subject to forfeiture if less than the full award vests over the 7 year performance measurement period. At the end of each calendar year, the Compensation Committee will determine the Company's pro-rated annual and cumulative total return to shareholders from 3/1/07 through the end of each calendar year. Vesting will occur at the end of each calendar year as follows (pro-rated for 2007): Annual and Cumulative Return per year both less than 9% - 0% vesting; Annual or Cumulative Return per year equal to or greater than simple 9% - 14.286% vesting; Cumulative Return per year equal to or greater than simple 9% - any portion that failed to vest in prior years.</footnote>
    </footnotes>

    <remarks>This filing adds the performance based awards made on August 7, 2007.  The time based awards vest on December 31 of each year.  The original filing stated this date as March 8 of each year.</remarks>

    <ownerSignature>
        <signatureName>Philip Summerlin, by power of attorney</signatureName>
        <signatureDate>2007-08-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
