KIRSTIE ALLEY collapsed while rehearsing for “Dancing with the Stars” – and faces life-threatening kidney problems!

The 61-year-old actress is pushing herself to the brink physically with grueling workouts for “Dancing,” while sticking to a strict diet in a desperate bid to slim down from 200 pounds, say sources.

Now medical experts warn her intense exercise sessions, combined with her unhealthy eating habits, put the former “Cheers” star at risk of deadly kidney failure.

“Kirstie is a complete wreck,” said a source. “She’s driving herself so hard that she’s making herself sick.

“She’s been sipping the Rescue Me elixir from her Organic Liaison weight-loss program and getting by on just one solid meal a day, usually a tiny portion of baked chicken or a salad with lemon juice, along with a few rice crackers.”

But Kirstie’s biggest problem is lack of hydration while overexercis­ing, said the source.

“When she was tapped for the ‘All-Stars’ season, Kirstie jumped back into hellish eight-hour rehears­als after months of doing only an occasional light dance routine,” said the source.

“She’s sweating heavily during her workouts, but she’s not drink­ing enough liquids to compensate. Her excuse for not hydrating is that she doesn’t want to gain any more water weight. She’s angry at her­self for falling off the dieting wagon months ago.”

Kirstie – who has pushed the scales at 230 pounds – first signed on with “Dancing” in 2011. By early that year the 5-foot-8 star claimed to have dropped to 140 pounds, and says she slimmed down from a size 16 to a svelte size 8.

But as The ENQUIRER has report­ed, Kirstie ballooned back up to 200 pounds while struggling to finish her upcoming memoir, “The Art of Men.”

“After her first run on ‘Dancing’ ended, Kirstie went back to some of her old bad habits,” said the source.

“She smoked cigarettes to kill her appetite, ate fatty junk foods when she was under stress and vegged out in front of the TV or the computer while working on her book.

“Kirstie claims to have maintained her 100-pound weight loss with an organic diet and daily dance work­outs, but that just isn’t true. She nev­er leaves the house without wearing Spanx, and she’s nowhere near her peak physical form.

“When she was invited back for the ‘All-Stars’ season, she panicked and went on a crash diet.”

Despite that, the pounds refused to melt away, and hefty Kirstie appears to be one and a half times bigger than her “Dancing” partner Maks Chmerkovskiy, who is 6-foot-2 but weighs 170 pounds.

Her health woes climaxed with a dramatic collapse after a killer re­hearsal session for “Dancing,” said the source.

“Kirstie had been pounding the boards for five hours in extreme heat when she abruptly announced that she needed a break,” said the source.

“Sweating profusely, Kirstie stum­bled to the dance bar and grabbed hold of it to steady herself. If she hadn’t grabbed that bar, she would have keeled over and hit the floor hard.

“Kirstie looked so out of it that an assistant came run­ning over and led her to a chair, where she broke down in tears. Someone immedi­ately suggested calling the paramedics to the ‘Dancing’ studio. But Kirstie wouldn’t have it. She didn’t want anyone to know about the incident.”

Afterward, Kirstie was photographed leaving the “Dancing” practice studio look­ing haggard and exhausted.

Later that day, she posted a mes­sage on Twitter saying that she’d had a tough day in rehearsal and had “cried like a baby no less than 5 times.”

Dr. Steven Lamm of the New York University School of Medicine, who has not treated Kirstie, warns the former “Fat Actress” is headed for disaster.

“It’s extremely unwise for her to jump into extreme dieting and ex­ercise after a period of inactivity,” Dr. Lamm told The ENQUIRER.

“Intense exercise stresses all the muscles. Not staying hydrated is also dangerous because as the muscles break down they release a protein called myoglobin.

“Without proper nutrition and hydration, myoglobin can build up in the bloodstream and damage the kidneys. This can absolutely lead to kidney failure.”

Severe dieting and intense exercise can also cause hypoglycemia, an ab­normally low level of blood sugar, he added.

“HYPOGLYCEMIA can lead to fainting, seizures or coma,” Dr. Lamm explained. “Kirstie needs to eat properly and drink fluids, especially during intense rehearsals, or she’s in danger of all the muscles of her body breaking down.”

Dr. Craig Title, a New York-based weight-loss expert, confirms the danger of intense exercise without proper hy­dration. “Lack of water with extreme workouts can lead to kidney-related problems,” said Dr. Title, who has not treated Kirstie.

“The added stress of a low-calorie diet on top of an extreme workout and low hydration can be dangerous.”

In addition to her health woes, Kirstie is also frustrated with the chilly reception she got from Dr. Mehmet Oz while promoting her Organic Liai­son weight-loss products on his Sept. 17 talk show. “Kirstie had every intention of getting Dr. Oz to endorse Organic Liaison,” said the source.

“But he wouldn’t go there, and she bad-mouthed him off camera to any­one who would listen.

“Kirstie needs to stop sweating the small stuff and focus on her health. If she doesn’t take better care of herself she could wind up in the hospital – or worse yet, the grave!”