So much so that he would only admit that a problem surfaced in 2014, and that the team doctors were able to correct it.
"I am a diabetic," the top-tier cornerback told The Arizona Republic this week. "Let's just keep it that way."
Peterson seemed to be uncomfortable at the mention of an issue. Arizona Cardinals coach Bruce Arians hinted at a problem during the season when he said Peterson was suffering from a blood sugar deficiency and that it was affecting Peterson's play on the field.
"Yeah, it did," Peterson said. "I'd rather not go into deep detail about that. It was a situation that it occurred during the season. The team docs found it and got it all under wraps."
"I want to take a moment to address the media reports this morning regarding my health," the cornerback tweeted. "While I did have abnormal sugar levels, I've been working with doctors on a strategic meal plan and workout routine that are reversing these symptoms.
"I'm grateful that this has been reversible for me and my health is back to normal. Thanks everyone for their concern and well wishes! Now back to my workouts and getting ready for the upcoming season!"
There's no doubt that we could see a big change in Peterson this year, especially if the diagnosis was unknown to him in the past, or he didn't have a good idea of how to handle it.
Depending on the type and severity, diabetes can cause issues across the body and nervous system, though plenty of NFL players including Jay Cutler, Mike Echols and Kendall Simmons have thrived despite their battle with the condition.
Peterson sounds confident that any blood sugar issues won't arise again in 2015, and it also sounds like he's done addressing it.