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John Carlson paused to consider a question about the number of concussions he has suffered in his football career, but he politely declined to give an answer.

“I’m going to pass on that,” he said.

This is a sensitive and serious subject for Carlson, the Litchfield, Minn., native and Vikings tight end. He has suffered three known concussions in six NFL seasons and, according to various reports, two additional ones during his college career at Notre Dame.

Carlson’s latest concussion occurred two weeks ago at Baltimore when he was slammed face first onto a frozen field. Carlson missed Sunday’s game against Philadelphia after failing to pass the NFL’s concussion protocol last week.

Carlson eventually passed the necessary steps to return and practiced Wednesday, but he didn’t feel well Thursday and was held out of practice. He must pass certain protocol again in order to be cleared to play Sunday at Cincinnati, according to coach Leslie Frazier.

Minnesota Vikings tight end John Carlson.

In a post-practice conversation Wednesday, Carlson said he and his wife, Danielle, will discuss his concussion history in depth after the season, and he indicated that retirement might be an option.

“That’s something that my wife and I will consider,” he said. “After every season it’s an evaluation period because of the nature of our business. Players move around, players get cut, coaches get fired, things happen. So in that sense, every year is an evaluation period and this year will be no different. And the concussion part of it will be in that conversation.”

Carlson has suffered three concussions since 2011. He turns 30 in May, and he acknowledged that his family is concerned about his long-term health and quality of life.

“We have two kids and a third one on the way,” he said. “I’m taking steps to mitigate the risks. [But] there are risks to playing football.”

Carlson said he’s sought advice and “assistance” from medical experts on concussion-related issues throughout his career. He has tried to be proactive in learning more about the injury, but he stressed that football always will have inherent dangers.

“I don’t know that anyone has a magic bullet,” he said. “It’s something that’s kind of evolving over time and as they research it more, I’m sure they will have better ways to treat concussions down the road. But I don’t think you can make the game safer to the point that there aren’t going to be concussions because it’s a physical game by nature. They take away helmet-to-helmet hits, but if you hit your head on the ground, what are you going to do? Penalize the guy for that? Pretty soon it’s not football anymore.”

As a member of the Seattle Seahawks, Carlson was knocked unconscious after trying to leap over a Chicago Bears defender in a playoff game during the 2010 season. He was carted off the field and taken by ambulance to a hospital. He said he felt normal two days later.

Carlson said he experienced a headache with his latest concussion but didn’t suffer any memory loss.

“I didn’t really feel abnormal, but it’s a serious thing,” he said. “If you have any symptoms, it’s not something you want to rush back from.”

Carlson signed a five-year contract worth $25 million with the Vikings last offseason. He finally found a meaningful role in the offense in recent weeks after Pro Bowl tight end Kyle Rudolph suffered a season-ending foot injury.

But now he is dealing with his fifth career concussion.

“It’s a serious issue and it’s not something that I’m ignoring,” he said. “I wouldn’t be playing if I didn’t feel that it was safe within the realm of safety and football, if there is such a thing as safety. We understand that there are risks associated with playing this game.”

The NFL now operates in an age of concussion awareness after numerous cases of former players who are dealing with traumatic brain injuries came to light. Carlson said he understands the potential consequences he faces later in life because of his concussion history.

“I know some former players that played for 15 years that are in their 80s,” he said. “And we all know of guys that have degenerative brain disorders in their 40s. It’s a scary thing, but it’s one of the risks that we take playing football.”