Hospital chain HCA Holdings (HCA) announced Tuesday the sale of up to $1.8 billion of stock in a secondary offering.

With stockholders prepared to sell about 50 million shares, the offering could return around $1.8 billion at the current market price of $36 a share. HCA said all proceeds will go to the stockholders putting shares up for sale.

No shares are being sold by HCA in the offering, which is set to close by Feb. 15.

Private equity backers KKR (KKR) and Bain Capital, which together hold a 50.3% stake in HCA, will receive most of the proceeds. Their ownership stake will drop to roughly 39.3% by the end of the offering.

In 2006, the firms invested about $4.9 billion in the company when it was purchased for $21.3 billion. HCA went public in March 2011.

Shares of HCA slid 56 cents, or 1.53%, to $36.10 Tuesday morning.

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