Her husband, Mr Ng Kheng Lim, hated the four-hour-long, thrice weekly dialysis sessions he needed to stay alive.
So, she gave him one of her kidneys.
That was 11 years ago. Now, husband and wife are doing well and have no regrets.
'I live with him. When he's not happy, I'm not happy,' Madam Tan, 60, said. 'But I would be lying if I said I wasn't afraid.'
Mr Ng discovered one of his kidneys was failing in 1994. The news came as a shock, as he was not diabetic. Aside from high blood pressure, which was well controlled, he had no other medical problems.
He was put on a strict low-salt, low-protein diet to extend the life of his fast-failing kidney. But by the end of 1995, the organ could not keep up with the strain and Mr Ng was forced to go on dialysis.
He hated it.
'You just sit there for four hours doing nothing. And I had to do it three times a week. Often, I didn't want to go.'
Although they have three adult children, Mr Ng, now 67, did not want to ask them or his wife for a kidney.
He explained: 'I didn't want to pressure her into giving me a kidney.'
He casually mentioned the subject of transplant to the coordinator at the National University Hospital, who then spoke to his wife.
She immediately agreed.
Said Mr Ng: 'My wife was very brave.'
SALMA KHALIK