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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-05-30</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001145460</issuerCik>
        <issuerName>INVERNESS MEDICAL INNOVATIONS INC</issuerName>
        <issuerTradingSymbol>IMA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001422158</rptOwnerCik>
            <rptOwnerName>Geraty Ronald D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>51 SAWYER ROAD</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>WALTHAM</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02453</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO, Alere Medical, Inc.</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-05-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>21987</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>34.34</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>45012</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On May 30, 2008, the reporting person was issued 21,987 shares of Issuer common stock pursuant to a purchase price adjustment provision in the merger agreement pursuant to which the Issuer acquired Alere Medical, Inc. The merger agreement provided that if the price of the Issuer's common stock was below $58.31 on May 16, 2008, then former Alere stock and option holders who continued to hold Issuer stock/options would be entitled  to an amount, payable in cash or stock at the Issuer's sole election, equal to the product of a) the number of Issuer shares/options then held and b) the amount by which $58.31 exceeds the greater of the price on May 16 ($33.32) or $43.73. On May 30, 2008, the Issuer exercised its option to pay this amount in shares of common stock based on a valuation of $34.34 determined pursuant to the merger agreement.  A total of 107,592 shares of Issuer common stock were issued pursuant to the purchase price adjustment provision of the merger agreement.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ron Geraty</signatureName>
        <signatureDate>2008-06-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
