MMAJunkie.com has the story:
White said Lesnar collapsed while spending time on a retreat in Canada and was checked into a hospital.
“[Lesnar] is in bad shape, and the reality is they don't really know all that's wrong with him,” White said. “He owns a bunch of property in Canada. He went up to Canada just to get away from his house, to go up there and just kind of chill out up there.
“He [expletive] dropped. He went down, and he had to go to the hospital. They ran every test on the planet on him, and they ended up finding out something else was wrong with him.”