The 54-year-old tennis legend was assisted down Mount Kilimanjaro by porters and driven to the Kilimanjaro Christian Medical Centre for assessment. The 27-person climbing team Navratilova was in has faced heavy snows and mist since beginning the climb up the 19,340-foot (5,895-meter) mountain Monday.
Navratilova was "in good spirits" but disappointed to leave the mountain, the sports charity said.
"The weather is a little better, but the going is getting tougher and tougher," Navratilova wrote in a blog posting on Thursday.
"It seems to be constantly steep and as we started to approach the highest point yet, 4,500 meters (14,765 feet) above sea level, sheer exhaustion sets in for much of the group, and with heavy legs and chests pounding due to a lack of oxygen, every step becomes an effort," she wrote.
Navratilova, who won 18 singles Grand Slams, told The Associated Press last weekend that she has never climbed higher than 12,000 feet. The Aspen, Colorado resident told AP she was "petrified" of failing to reach the summit "because then the whole world will know."
Navratilova was climbing the mountain to raise money and awareness for the Laureus Sport for Good Foundation. The rest of the team will continue the climb and should reach the summit Saturday.