Dr. Oz's Mother Has Alzheimer's: 'I'm Feeling Guilty Because I Completely Missed the Signs'

Dr. Mehmet Oz has learned that his mother, Suna Oz, has Alzheimer’s disease, a “gut punch” for the doctor, who says that he “completely missed the signs.”

The host of The Dr. Oz Show, 59, says that he is “frustrated and mad” at himself for not recognizing that his 81-year-old mother’s health was failing.

“I’m feeling guilty because I completely missed the signs until fairly late in the process,” Oz tells PEOPLE.

Oz, whose father died in February, says that he and his two sisters noticed different irregularities in their mom’s actions — Oz saw that she was struggling to find her words, while his sister thought she was dressing oddly. But the siblings did not put the signs together.

“If the right word was, ‘You look beautiful today,’ she would use, ‘You look pretty prettier today.’ I missed those clues,” he says. “Alzheimer’s is like a snake in the grass. You don’t see it. You only see the effects of it suddenly. And if there’s a wind blowing the grass, you don’t even notice the grass moving strangely. It sneaks up on you.”

Oz says they started to realize that something was wrong because Suna, who was already stubborn, started becoming irrational.

“The stubbornness transitioned from just her being an opinionated person to, ‘Hey, that’s dangerous medically. I can’t let you do that,’ ” he says.

The family took Suna for testing, and doctors confirmed the Alzheimer’s diagnosis. She is now living in Turkey, her home country, under the care of Oz’s sister. He says it has been difficult to see Suna struggle with her memories.

“She’s aware, but she’s forgetting some things,” he says. “Daphne [Oz’s daughter] had a baby girl 20 days ago and I called mom to tell her. She knows Daphne, but she couldn’t quite process that Daphne had a child.”

Oz says the mom that has been there for him throughout his life is disappearing.

“These are not normal things from my mom. And that’s the most painful part of this whole process because I end up losing my mom twice,” he says. “The woman that I love whose bright eyes were there for every experience I’ve ever had as a child — those eyes are starting to dim. The light that that made her who she was is starting to go out.”

“As she stops knowing what I’m talking about, as her memories evaporate, she stops being my mom. And then her body will still be there, and obviously I love that body, but it won’t be the same as loving my mom. And then years later you actually bury the person.”

Oz says he “debated long and hard” about whether to share his mom’s diagnosis, but after learning that there are 6 million Alzheimer’s patients in America and 16 million caregivers, he realized it was important to speak out. He will share the news on Monday’s episode of The Dr. Oz Show.

“I know that there are millions of other people like me, who probably feel guilt the way I do, knowing that if we could have figured this out earlier I could have intervened a little bit,” he says.

“The worst lies are the ones we tell ourselves,” he says. “Everyone in my family probably could’ve figured this out, myself included. But my wishful thinking was that it was just mom being a little bit older, she’s stressed out, my dad was ill. And so we lost our truth.”

Through this ordeal, Oz also learned that he carries one of the genes for Alzheimer’s, a trait he shares with one in three Americans.

“That was shocking,” he says. “I guess you don’t expect it. But from my perspective, my mom gave me a great set of cards to play life with and she taught me how to play those cards. But she gave me one bad card and I can’t throw that card away, I’m stuck with it.”

He plans to work on preventative measures like watching his belly fat and keeping his mind sharp. And as his mom loses her memory and functions, Oz will remember all she did for him.

“I’m thinking about how much she’s accomplished in her life and what a pleasure it was having her as my mom,” he says. “I am able to do what I do because of her.”

The Dr. Oz Show airs weekdays. Check your local listings.