A transit worker who helps to keep the subway system alive has now done the same for an ailing co-worker, with an organ donation that saved two people. NY1's Jose Martinez filed the following report.

Track workers George Muehlhaus and Victor Rivera are back on the job at the 38th Street Yard in Brooklyn, a long way from the chat that helped to save Rivera's life.

"I was sitting at my desk and he came up and said, 'Hey, how did the kidney stuff work?' And so I explained to him, and he was like, 'Oh, you know, why don't you give me the number.'" Rivera said.

In 2013, Rivera was diagnosed with kidney failure. Doctors said he would need dialysis and, one day, a transplant, to save his life.

He and Muehlhaus have known each other since they were rookie track workers in Queens 17 years ago. But they were just acquaintances for most of that time, which made Muehlhaus's offer to donate a kidney all the more surprising.

"It's not like a co-worker is lending me $10," Rivera said. "I mean, it's literally saving your life."

Muehlhaus' kidney was not a match for Rivera, but he decided to become a donor anyway. That allowed his friend Rivera to move up on a nationwide transplant wait list. 

"I did not really mind giving my kidney to somebody else as long as Victor would get a kidney," Muehlhaus said.

Also motivating Muehlhaus: a desire to get in shape. Doctors said he had to lose weight to become a donor.

In July, a matching organ became available for Rivera. He got his new kidney at Mount Sinai Hospital, and Muehlhaus gave one of his away.

"Here's somebody who saw a need, saw somebody who had a need and he decided to step up," Rivera said. "You know, that's the incredible part, that he actually saved two lives. Because there's a guy in Indiana right now who's not going to dialysis, who has a future because of George."

Muehlhaus was back on the job in August. His friend returned this past Monday.

"I haven't been to dialysis since July 12, so I got 20 hours of my life back a week," Rivera said.

"His whole demenaor changed right from the get-go," Muehlhaus said.

And after what began as a combination weight loss plan and organ donation idea, Muehlhaus has now lost 37 pounds since he hatched the idea to help out a co-worker. 

Co-workers, and now, they say, lifelong friends.