Chrissy Teigen and John Legend's eldest son has been diagnosed with Type 1 Diabetes.

The 38-year-old model had sparked questions from fans when she shared a photo over the weekend of older children Luna, eight, and six-year-old Miles cheering on Team USA and many noticed the little boy had a glucose monitor on his arm, and she's now thanked her followers for their "beautiful and incredible" words of support and encouragement as she confirmed the condition, which affects the body's ability to produce insulin.

She wrote on Instagram: "A lot of you noticed something a little special about a photo I posted a few days ago — Luna, Miles and I celebrating Simone and team USA.

"Miles had his arm up, and soooo many of you reached out to say the most beautiful and incredible words I have ever witnessed on this platform.

"You noticed his type-1 diabetes monitor and extended so much love and encouragement in every way possible. I was, and am, so blown away by the kindness of this community, already.

"I know. Things could be so much worse!! So many parents around the world are going through unfathomable things that I could never imagine.

"I tell myself this every time we get a red alert blasted to our phones. And we are so blessed to have so much help and a wonderful, kind, huge-hearted specialist."

The 'Lip Sync Battle' star - who also has Esti, 18 months, and Wren, 13 months, with John - explained the condition was detected by chance after Miles and his friends contracted a sickness bug and required blood tests.

She wrote: "A couple weeks ago, our Miles was sick, in the hospital, with a terrible case of shigella, an intestinal infection caused by bacteria in food or water. A lot of his friends were also sick with it, as they went to the same camp and well, it happens!

"But the doctors knew something else was off about his blood tests. I've learned since then that this is how so many young children end up being diagnosed with type-1 — going to the hospital for something completely different.

"After more testing, we learned he is in the 'honeymoon period' of a lifetime of T1.

"Last night we gave him his first shot of insulin and here we go! A different, new world for us and we are certainly learning so much on the fly.

"This post is to thank you so much for your kindness. It helps Miles so much to know so many other people are going through the same thing and he is not alone."