Activist investor Carl Icahn revealed an increased stake in WebMD Health Corp , a day after the company adopted a shareholder rights plan.

On Wednesday, WebMD, which provides health information to doctors and other consumers through its online portals and mobile platforms, adopted a rights plan that was designed to keep away inadequate or coercive takeovers, with the trigger set at 12 percent.

In a regulatory filing, the billionaire fund-manager revealed a stake of 9.49 percent in the company, up nearly 1.5 percent points, from the shareholding he declared on Oct 21.

Icahn's stake now is the largest single position in the company.

Icahn's investment in a company usually precedes a demand to either bring a change in the company's management or a proposal to consider strategic alternatives, including a sale or merger of the company.

George Soros-owned Soros Fund Management Llc said it owned about 8 percent in the company, two days after Icahn's announcement in October.

WebMD shares slipped 2.5 percent to $30.36 in extended trading. They closed at $31.15 Thursday on Nasdaq.

(Reporting by Vidya L Nathan in Bangalore; Editing by Supriya Kurane)