Wellens, signed on loan by former Town boss Paul Jewell, returned to the King Power Stadium last week following the end of his month-long stay at Portman Road.
McCarthy, who recently succeeded Jewell, is keen to bring the 32-year-old back to Suffolk and has spoken to Leicester counterpart Nigel Pearson.
"He hasn't got a big squad," McCarthy told BBC Radio Suffolk.
"It's up in the air at the moment. We can do it next week if we feel we should and if they want to do it.
"We're beholden to Leicester - he's their player."