The Sweden great has only made five Premier League appearances this season after suffering a major knee injury in April, and is currently sidelined as he continues to work towards full fitness from that setback.
However, Mourinho says that veteran Ibrahimovic has had plenty of opportunities to tell him if that is the case and is taking his silence that no news is forthcoming.
"I don't speak with players about media news," he told a news conference ahead of United's Premier League contest against Huddersfield Town.
"I see him every day, I'm not working directly with him but for example I was with the fitness coaches watching his work, he's with me before and after training and never mentioned anything to me.
"Not an opinion, comment, nothing at all, so I presume nothing is true in the news because I would probably be first to know from him, so I presume nothing."
United fell 15 points adrift of leaders Manchester City with a poor showing in Wednesday's 2-0 defeat to Tottenham, a match that saw Marouane Fellaini brought on as a substitute and taken off again due to a knee injury.
"It is not an ACL [anterior cruciate ligament injury], not a complete rupture of any structure of the knee not as far as that," he added.
"But we need him, the Champions League is arriving, lots of tough match and probably we will lose him for a few weeks – two, three, four? I don't know."