Lomu was being treated with daily dialysis as doctors tried to repair the kidney he was given by friend and ZM radio host Grant Kereama.
Tests were carried out to see whether the transplanted kidney could be revived, but it is not known whether it could be saved.
The former All Blacks winger and rugby superstar was discharged from Auckland Hospital's renal unit on Monday afternoon.
Days after he starred in the Rugby World Cup opening ceremony, Lomu was rushed to hospital after it all "went pear-shaped".
"I was just about to leave for a function and I crashed. My kidney was failing, and my body had become toxic. It started to shut down," he told the New Zealand Woman's Weekly.
He was told there was a slim chance his kidney would survive.
Lomu was diagnosed with the debilitating kidney disorder, nephrotic syndrome, in 1995, a year after his All Black debut.
In 2004, he received a transplant from Kereama which helped return him to good health, and he had recently been training for the Fight for Life boxing match.
Lomu was still on the bill last night and is set to get in the ring with heavyweight David Tua on December 23.
Medical experts have poured cold water on the suggestion Lomu's intense boxing training contributed to his hospitalisation.
New Zealand's deceased donor waiting list has about 600 people on it, with an average wait time of three years. The rarer the person's blood type, the longer the wait.
If Lomu loses his kidney, the All Black hero is unlikely to be short of offers for a new one. His wife, Nadene, immediately offered one of her own, if compatible.
Nadene Lomu, who is also her husband's manager, did not return calls last night.
- The New Zealand Herald
