From what age can you identify diabetes in children? If I suspect my three year old has diabetes, are the tests 100% reliable?

Blood sugar levels can identify clinical diabetes at any age.

You don’t say whether there is a positive history for diabetes in your family. That’s very important because the issue of the magnitude of risk of a child with family history positive for type 1 diabetes (genetic component of the risk) hasn’t been fully clarified yet. In your son’s case, we might say it’s not higher than 6%. In order to detect the possibility for future diabetes, the doctors could check him for autoantibodies If this latter test would turn out to be positive, the doctor may want to add an IVGTT in order to increase reliability of the test.

The tests never reach 100% of what we call the Positive Predictive Value.

MS