Earnings (loss) per Share (Tables)

3 Months Ended

Mar. 31, 2015

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The following table sets forth the computation of basic and diluted earnings (loss) per share for the threemonths ended March 31, 2015 and 2014:

	Three Months Ended March 31,
	2015		2014
	(in thousands, except per share amounts)
Basic and diluted
Net income (loss) attributable to The Medicines Company	$	5,034	$	(4,996	)
Weighted average common shares outstanding, basic	65,174		64,152
Plus: net effect of dilutive stock options, restricted common shares and shares issuable upon conversion of convertible senior notes due 2017	1,755		—
Weighted average common shares outstanding, diluted	66,929		64,152
Income (loss) per share attributable to The Medicines Company, basic	$	0.08	$	(0.08	)
Income (loss) per share attributable to The Medicines Company, diluted	$	0.08	$	(0.08	)