High-functioning and low-functioning aren't even diagnoses or specifiers. They were informal labels given based on whether someone's IQ was above 70 or below 70. The problem is that, especially in people with autism, IQ tests aren't very useful, either because someone is unable to communicate what they know, or they have what's called a "spiky" profile, like me, where they have uneven skill sets, making a full-scale IQ invalid. The other reason the high-functioning label was given was for people with what is considered "milder" autism. People who can speak fluently, function (with some support), and generally had a "good" prognosis. On the other hand, people with "severe" autism are often considered "low functioning" because they have higher support needs. The problem nowadays is people think of the autism spectrum in a linear way. I have moderate classic autism but that doesn't mean I sit in between "mild" and "severe" autism. I have moderate to high support needs, yet I am considered intelligent. So do I have LFA or HFA? Exactly, the answer is neither. The next time someone tries to peg you with a functioning label, this is all the information you need. You don't have to "prove" your autism, even if it is considered mild. People with mild autism are fully autistic, just lower support needs. People with moderate or severe autism have higher support needs. But we all have autism.