UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No.     )

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Filed by a Party other than the Registrant  o

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Preliminary Proxy Statement

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Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

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Definitive Proxy Statement

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Definitive Additional Materials

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Soliciting Material under §240.14a-12

The Medicines Company

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

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Total shares underlying options outstanding under the Company’s stock incentive plans at March 31, 2013 (excluding the Company’s 2000 and 2010 employee stock purchase plans):

8,617,383

Weighted average exercise price per share of outstanding options:

$20.80

Weighted average remaining contractual term of outstanding options:

6.23 years

Total outstanding shares of restricted stock awards granted under the Company’s stock incentive plans as of March 31, 2013:

638,455

Total shares available for future grant under the Company’s stock incentive plans at March 31, 2013 (excluding the Company’s 2010 employee stock purchase plan):

775,628