Vardy, who can equal the Dutchman's mark of scoring in 10 straight games if he nets at St James' Park, missed England's friendlies with Spain and France because of a hip injury.
The 28-year-old is back training and eyeing Van Nistelrooy's 2003 feat for Manchester United, but Ranieri, who joined Leicester in July, is looking long-term.
"I speak to the doctor. If he's 100% he plays," the Italian told reporters on Thursday.
"I don't want to risk a player for a match then lose him for a month. I'm not thinking about (who takes) penalties or records. I'm thinking about Newcastle. It will be a tough match."
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Leicester are third in the Premier League table, one point behind Manchester City and Arsenal, who both have 26 points.
Ranieri, who has also had spells in charge of Chelsea, Juventus and Inter Milan, said the secret to his side's success this season was "Italian tactics and English spirit".
"I want to work hard to improve both with Leicester," added the 64-year-old, who said his prime target was reaching the 40 points traditionally regarded as the minimum required to avoid relegation.
"We are fighting for another 15 points. Every match is a trap. Newcastle are a good team with good fans who push their players, but we are ready."
Newcastle are two points clear of the Premier League relegation zone in 17th place out of 20 clubs.
(Reporting by Rob Hodgetts,; Editing by Neville Dalton)
