The 40-year-old Englishman has been suffering from arthritic problems in his right foot and missed his last two cuts on the PGA Tour.
"I am obviously disappointed to be in this situation, especially during a Ryder Cup year," Poulter said.
"Right now, rest and rehab take priority."
Poulter has competed for Europe at the past five Ryder Cups, taking 14 points from 18 matches.
He is ranked 85th in the world and his last tournament win was the HSBC Champions in 2012.
Because of his low ranking, Poulter probably would have had to rely on Europe captain Darren Clarke selecting him as one three wildcard picks.
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Ian Poulter's hopes of playing in September's Ryder Cup are in doubt after he said he would be out of action for four months with a foot injury.