-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 Bd62ItGbV5qZZ4Gyr+ZQ3D/v+9QGZhFC8g5s+BAuAjrvSYIGvAkIxSVGiWcfXNwR
 ITd966PogpdNUH6oEsM/5A==

<SEC-DOCUMENT>0001140361-10-048642.txt : 20101207
<SEC-HEADER>0001140361-10-048642.hdr.sgml : 20101207
<ACCEPTANCE-DATETIME>20101207165159
ACCESSION NUMBER:		0001140361-10-048642
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20101201
FILED AS OF DATE:		20101207
DATE AS OF CHANGE:		20101207

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			GUPTA RENU
		CENTRAL INDEX KEY:			0001269592

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-30739
		FILM NUMBER:		101237753

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			INSMED INC
		CENTRAL INDEX KEY:			0001104506
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				541972729
		STATE OF INCORPORATION:			VA
		FISCAL YEAR END:			1201

	BUSINESS ADDRESS:	
		STREET 1:		8720 STONY POINT PARKWAY
		STREET 2:		SUITE 200
		CITY:			RICHMOND
		STATE:			VA
		ZIP:			23235
		BUSINESS PHONE:		804-565-3000

	MAIL ADDRESS:	
		STREET 1:		8720 STONY POINT PARKWAY
		STREET 2:		SUITE 200
		CITY:			RICHMOND
		STATE:			VA
		ZIP:			23235
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 3
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0203</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2010-12-01</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001104506</issuerCik>
        <issuerName>INSMED INC</issuerName>
        <issuerTradingSymbol>INSM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001269592</rptOwnerCik>
            <rptOwnerName>GUPTA RENU</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>11 DEER PARK DRIVE, SUITE 117</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MONMOUTH JUNCTION</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>08852</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP of Development &amp; CMO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>No securities are beneficially owned.</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Renu Gupta</signatureName>
        <signatureDate>2010-12-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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