WATCH: Heather Rae Young Holds Tarek El Moussa's Hand as He Finds Out He Has Celiac Disease
Tarek El Moussa has been diagnosed with celiac disease, and his fiancée Heather Rae Young has been there to support him from the start.
In an exclusive sneak peek, above, of Thursday night's episode of El Moussa's solo HGTV show Flipping 101, the father of two discovers he has celiac disease after undergoing several blood tests at his doctor's office.
"It turns out you have celiac," Internal Medicine Specialist Dr. Ellen Song tells El Moussa, 40, as he holds hands with Young, 34.
El Moussa slowly nods his head at the news as the Selling Sunset star, 34, turns to him and quips, "You don't even know what that is!"
"No idea what that is," he admits with a smile, as the doctor says, "You have a gluten allergy," and explains how the disease works.
RELATED: Tarek El Moussa Reveals His Original Wedding Plans & Why They 'Completely Changed'
Dr. Song adds, "If you stay gluten-free, one, you'll feel better and two, the risk of cancer is much, much lower."
El Moussa is already a two-time cancer survivor, having endured battles with both testicular cancer and thyroid cancer.
"So, my favorite foods or living better and healthier and longer?" El Moussa asks. He then looks to Young, who has been vocal about her vegan diet, and asks, "Gluten is in everything. What am I gonna eat?"
HGTV Tarek El Moussa
In a separate on-camera interview, the Flip or Flop star says, "I wasn't really expecting that news and it's just gonna be a really big change for me. But the good news is I know what's wrong and hopefully things will get better."
RELATED: Tarek El Moussa Tests Positive for Breakthrough COVID, Is Quarantining with Heather Rae Young
Last November, El Moussa opened up to Daryn Carp on an episode of PEOPLE TV's Reality Check about how Young, to whom he proposed to in July 2020, has been a positive influence on his health throughout their relationship.
"Heather has made a lot of changes in my life. She feeds me, cooks for me, she tells me what to eat, she makes sure I'm taking my vitamins. She's all over it," he said at the time.
El Moussa also noted that in 2020 he felt "healthier than I've ever been in my life."
Tarek El Moussa/ instagram
"I've never eaten so clean, I've never taken so many vitamins, I've never gotten so much exercise. So I'm just taking care of my health. I want to live. I want to live for my kids. I want to live for my grandkids," he said. "You only get one life. You only have one body."
El Moussa shares daughter Taylor, 11, and son Brayden, 6, with ex-wife Christina Haack.
RELATED: Tarek El Moussa and Heather Rae Young React to Christina Haack's Engagement: 'Wow, Awesome!'
Tarek El Moussa/Instagram
RELATED: Tarek El Moussa Celebrates Fiancée Heather Rae Young's Birthday: 'My Best Friend in the World'
El Moussa recently suffered another health scare last week.
The Flipping 101 host, 40, received a positive COVID test result during regular on-set testing, his rep told PEOPLE on Tuesday. He has since received multiple negative tests along with the positive test, but decided to immediately postpone filming in order to keep everyone safe. TMZ first reported the news.
Young has also undergone multiple tests which have all come back negative, but the pair are currently quarantining together out of an abundance of caution.
This will impact their filming schedules for Selling Sunset and El Moussa's two HGTV shows, Flipping 101 and Flip or Flop, which El Moussa co-stars in with Haack.
Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.
According to their rep, both El Moussa and Young are fully vaccinated, and "the couple has taken all necessary precautions to keep everyone safe." This includes sending El Moussa's two kids to stay with their grandparents (El Moussa's mom and her husband) in order to minimize their risk of possible exposure.
"Tarek is listening to the advice of his doctors and won't be scheduled to return to filming until he tests negative and his quarantine is complete," said the rep.