Lomu received a new kidney in a five-hour operation in Auckland on Tuesday. Today he was reported by his doctor to be doing well.
"He is still a bit sore but he is progressing as well as the surgeons could hope," said Dr John Mayhew today.
"He is talking. He is back to his normal self. He knows what is going on. He is not on a ventilator or anything like that. He is moving around, getting out of bed, albeit with difficulty at this stage," Dr Mayhew told Newstalk ZB.
Lomu's nephrotic syndrome kidney disease, diagnosed in 1995, eventually forced him out of the All Blacks and he has been on a dialysis machine for daily blood cleansing since last year.
The name of the donor has not been released.
Dr Mayhew said Lomu's surgeon had given him tacit approval to play rugby again but that was a decision Lomu would have to make.
"As a doctor I am hoping Jonah gets back to full health and can do all the things he wants to do.
"Now if one of those is playing rugby . . . he has discussed it before with the transplant surgeon and was given tacit approval for that," Dr Mayhew said on TVNZ.
But Jonah may realise that life off the dialysis machine is a much better thing than life on it.
"Whether he was to take the risk of playing risk of playing rugby with a transplant kidney . . . he is on record as saying he wants to and I believe he wants to.
"But obviously we get through the other things first and then decides what happens. It certainly hasn't been ruled out but I think we have got more immediate concerns," Dr Mayhew said.
Dr Mayhew said Lomu still had a lot of barriers to overcome before he could consider playing rugby again, including the major surgery and the possibility of the rejection of his new kidney.
"In three months we will have a better indication of the overall success of the operation but there are a number of hurdles to get over before we go that far."
He said the decision on the transplant surgery was made a couple of weeks ago but was kept quiet to give Lomu the best chance of recovering from the nsurgery without pressure.
"Very few people knew about this procedure for obvious reasons until several hours ago."
He said Lomu was a tough character and with the support of his family was making good progress as they helped him through a difficult time.
Serious contact sport for a transplant patient was not recommended by the New Zealand Kidney Foundation.
Foundation education officer Carmel Gregan-Ford said patients had their new kidneys implanted in the front of the abdomen where it was more vulnerable to physical damage from a tackle or a hit from a ball.
"Contact sport of any sort with a transplanted kidney isn't recommended. It is not something that is recommended by anyone I know," she said.
"We would recommend probably against it just because of the risk to the transplanted kidney."
She said Lomu would be on anti-rejection drugs for the rest of his life but the drugs would raise his risk of infection.
"'Because the drugs they are given are immuno-suppressants they suppress the immune system which means that stops the body from fighting the foreign kidney that is in there.
"The system is suppressed so consequently the person with the transplant is more at risk of developing infections and things like that so they have to be very careful avoiding infections and injuries."
However, she said if Lomu returned to rugby he would be very fit and that would count in his favour.
"If anybody was going to do it I suppose it would be Jonah but in the renal world, the kidney world, we wouldn't recommend somebody to go back to a contact sport, purely because of the risk of the kidney being damaged, particularly with it being hit or infected."