I believe there are actually six different auto-antibody tests that would help rule out type 1 diabetes. GAD is only one of those six and you may still test positive for some of the others. One of our members, @Melitta, is the resident expert on securing a correct diabetes diagnosis. Here’s her list of auto-antibody tests that may help clarify your diagnosis:
Get the full suite of autoantibody testing (Glutamic Acid Decarboxylase Autoantibodies (GADA), Islet Cell Cytoplasmic Autoantibodies (ICA), Insulinoma-Associated-2 Autoantibodies (IA-2A), zinc transporter (ZnT8), and Insulin Autoantibodies (IAA, Footnote 2).
Here’s the link for the full post. Melitta has written many comments and posts here about diabetes misdiagnosis, often based merely on age and body type. She knows what she’s talking about. Do a TuD search for her comments – use the magnifying glass icon in the upper right corner of your screen.