The Israeli midfielder signed with the Hoops from FC Ashdod at the end of August but has been with his national team and has not yet linked up with his new club.
Biton will join the Celtic squad in Milan ahead of the opening group stage game but Lennon suggests he is probably a bit underdone to take on the Italian giants.
"Nir Biton will travel but he hasn't trained with us obviously. We will have a look at him on Tuesday and see what sort of condition he is in," said Lennon.
"I don't think he played any football when he was away with Israel so it might be too soon for him."