"Star has a stress reaction in his foot," Panthers head athletic trainer Ryan Vermillion said in a statement. "We are going to be cautious. He is in a walking boot and we will reevaluate his foot in a few weeks."
It's the same foot that Lotulelei fractured in January, preventing him from playing in the team's NFC divisional playoff game against Seattle.
Asked if he thought he would miss time due to the injury, Lotulelei said: "I don't know."
Panthers coach Ron Rivera said the 2013 first-round draft pick has been experiencing soreness in the ankle and was taken to the locker room as a precautionary measure.
"His foot got sore, and the best thing is Dr. [Robert] Anderson happened to be in town, so we just gotta get him up and take a look at him," Rivera said.
Rivera added: "We might be being overly protective about it."
Lotulelei, considered a space eater in the middle of Carolina's defensive line, had 27 tackles and two sacks last season.
Carolina's other starting defensive tackle, Kawann Short, has missed the first four days of practice with back spasms. Rivera said Short is close to returning.
ESPN.com Panthers reporter David Newton and The Associated Press contributed to this report.