The 29-year-old former NFL Pro Bowler was at a Hollywood club -- The Colony -- Sunday night when the incident occurred, law enforcement officials, whose names were not reported, told the Los Angeles Times.
Merriman was transported to Cedars Sinai Medical Center about 9:30 p.m. local time, the officials said. Police initially gave no details beyond saying he had a "medical emergency."
His Twitter feed was active throughout the evening, with Merriman remarking on having lost a pair of sunglasses and ruining a shirt.
Merriman played six seasons for the San Diego Chargers and two for the Buffalo Bills before the Bills cut him prior to the 2012 season. He was later brought back to Buffalo to finish the year but retired thereafter at age 29.
Merriman said he wanted to leave on his own terms while could "still physically play the game."
He was drafted in the first round in 2005 out of Maryland.