"I had low blood pressure when they tested me at the gym.
"I was put in an ambulance and had a whole lot of fluid pumped into me on the way to hospital, saline solution and things, and my blood pressure was back to normal by the time I got to the hospital.
"I was under observation for 24 hours, but released on Friday.
"There's no issues there."
Williams - who has been on our screens since 1979 - said in April he had upped his fitness regime after piling on a few kilos. "I'm about two or three kilos heavier than I want to be," Williams said. "I like to be about about 84 to 85kg and I found out yesterday I'd fattened out to 87."
In 2011, the sports-mad presenter raised over $8000 for a cancer charity, after completing a half triathlon in Tauranga.
In November, explaining a plaster on his forehead, he revealed live on air he had a skin cancer removed.
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Williams, who usually spends part of his week in Mount Maunganui, spent last week in the South Island but planned to return to the Mount next week.
He was due back on screen this weekend and was keen to play down the latest health scare.
"It's been a fairly busy few weeks with a few things on, so it's just a warning to take it easy," he said.
TVNZ spokeswoman Georgie Hills said Williams' week-long break was a pre-arranged holiday and that he would be back reading the news tonight.
"Peter also filmed an episode of Mastermind New Zealand last weekend and he is as fit as a fiddle.":
