John Key has revealed doctors ran an annual full-scale health check on him last week and says the results show he is in "perfect nick".
Mr Key, 55, said he went through a "full bank" of tests including an assessment of his heart - and was given an all-clear.
"Totally. They run everything as you would expect. Perfect nick," the Prime Minister said.
"Every year they run a full bank of tests on me. They probably do a bit more than what would necessarily be the case for my age. But I just take the view that it is good to be cautious about these things. They've run everything on me from looking fully at my heart to making sure I pass every other test."
Mr Key makes an effort to keep fit, regularly working out in Parliament's gym.
He was responding to questions about the health of US Presidential candidate Hillary Clinton, who fainted this week because of pneumonia.
Mr Key has also fainted before, just before a trip to Antarctica in 2013.
"In my case it was out of the blue - they had a series of tests because I was going to Antarctica and I got through those with flying colours. After I fainted they ran the tests all again and it didn't show up and it's never happened again. I don't know, maybe [fainting] is just the rough and tumble of the job." Labour leader Andrew Little said he did not have a specific health test, but has had his PSA levels regularly checked after having prostate cancer six years ago.
Mr Little said he was a "picture of health".