Shares of McKesson (MCK) - Get Report are being hammered Friday, down 25%, as the stock fell to its lowest point since 2013. 

The company missed on earnings per share and revenue expectations and guided for a horrendously lower 2017 earnings result. This was one of the biggest guidance cuts TheStreet's Jim Cramer said he has ever seen. 

Speaking on CNBC's "Mad Dash" segment, the co-manager of the Action Alerts PLUS portfolio said he appreciated management's honesty on the conference call when executives said competition has increased so much that it's taking a big toll on the bottom line. 

McKesson needs drug prices to increase in order to boost margins. With no price inflation coupled with the increased competition, earnings per share are expected to take a big hit. Cramer said this was a huge surprise.

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But he wonders whether investors are overreacting in response to the news. 

Shares of McKesson were also downgraded by Deutsche Bank and Leerink, both of which can be read here

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At the time of publication, Cramer's Action Alerts PLUS had no position in companies mentioned.