Autoimmune diabetes in adults is often first treated as type 2. GAD antibodies are the most sensitive single test, and a low or falling C-peptide supports the picture. Typical clues are a lower BMI, a personal or family history of autoimmune disease, rapid failure of oral agents, and early need for insulin.
A positive result changes the plan: avoid relying on sulfonylureas, which may hasten beta-cell loss, keep a low threshold to start insulin, and teach ketone awareness. Testing everyone is not necessary; testing when the story does not fit is.
- Consider GAD antibodies when an adult with 'type 2' is lean, has other autoimmune disease, or fails oral agents within a few years.
- Pair the antibody test with a C-peptide to judge how much beta-cell function remains.
- If positive, plan for insulin and avoid depending on sulfonylureas.
- Teach ketone awareness to anyone with confirmed autoimmune diabetes.
Why it matters
Missed autoimmune diabetes leads to years of failing oral therapy and avoidable hyperglycaemia.
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