THE LAST we'd heard from Natalie Cole was last spring, when she was on CNN's "Larry King Live" talking about her dire health situation and how she needed a kidney transplant.

She'd contracted hepatitis C, a liver disease spread through contact with infected blood, most likely through her years of IV drug use. So, when I heard that the 59-year-old singer was going to perform in Philadelphia tomorrow night at the Keswick Theater, my first thought was, would she be up to it? She underwent a kidney transplant just this past May. And even before she'd had the lifesaving surgery, she had looked frail.

"I'm feeling really well," Cole told me during a phone interview. "I got my energy back, and my strength. It's really amazing. It's amazing. I didn't understand how sick I was until I got better."

The daughter of legendary crooner Nat "King" Cole had been on Interferon treatments when her kidneys failed, forcing her into dialysis three times a week. Since she was promoting her latest album, "Still Unforgettable," in far-flung spots around the globe, she had to find treatment centers so she could stick to her dialysis schedule.

Then, last spring, she went on King's show to talk about her plight, acknowledging that she'd brought her health problems on herself and now, without a transplant, she'd need dialysis for the rest of her life. Callers inundated the show to offer Cole a kidney, which didn't strike me as fair considering all the people in her same situation who didn't have the option of going on TV to publicize their need for new organs. Patients can wait for years for a transplant.

But Cole appeared humbled by the outpouring of support.

"That was amazing. These are the times you find out that people's hearts are in the right place," she told me. "I think it's an awesome testimony of human nature."

In the end, she found a match.

"Her family specifically bequeathed that kidney to me,: Cole said. "We are not that sure how it happened. Someone they knew was with me when I was on dialysis. I still haven't gotten the whole story."

The singer's relief at having found a donor, though, was tempered by the fact that her adopted sister, Carole "Cookie" Cole, was hospitalized in critical condition. In fact, Natalie had been in her sister's hospital room when the calls started coming in from the transplant center.

Carole, who had been diagnosed with lung cancer just two weeks earlier, died while Natalie was being prepped for transplant surgery. But Natalie's family didn't notify her until after the procedure had been completed.

Afterward, Natalie struggled with survivor's guilt. She and her sister had been best friends.

"It was hard to comprehend that something like this would happen. That's when I talked with God and said, 'What are you doing?' "

She got through it, though, and last month returned to the stage, performing at the Hollywood Bowl. According to the Los Angeles Times, she wowed the audience and told them, "I never thought I'd be standing here healthy, whole and 100 percent again."

While I still had her on the phone, I asked her what she'd learned from her experience.

"You need to be grateful every day and when the tough days come . . . and they will, you've got to be prepared for that as well," she told me.

"There's no magic. This is about putting one foot in front of the other."

Natalie Cole performs at the Keswick Theatre in Glenside, Keswick Avenue near Easton Road, at 8 tomorrow. $59.50. Tickets available through Ticketmaster.com or by calling 800-745-3000.