Absolutely! My son was 15 when he was diagnosed. There are members here who were dx in their 20's, 30's & 40's, believe it or not. My son's symptoms were mild and a-typical, so it wasn't so obvious. Of course, hind-sight is 20/20, so now I know why he had certain previously unexplained symptoms.
Is it you who is being tested or your child? I hope you find the answers you are looking for. Let us know what happens.
Stacey