I think sometimes that actually getting a true diagnosis can be overwhelming, and can be frustration, relief and frightening, all at the same time. It can be similar to situations through life (and grief).
But for me, even with my endocrinologists knowledge. I was out of my depth, and didn't have a clue. For someone in his late fifties, my doctors convincing me with T2, more than a decade previous. I was left with very little knowledge, and left floundering to understand what I had left myself into.
In other words, not a Scooby!
It took a lot of research and guidance, patience and an awful lot of trial and error to find a way to control the condition which would improve my health and symptoms.
I would definitely say that heightened anxiety after a diagnosis which is so surprising and a trip into the unknown, is not so unthinkable!