The Three Diagnostic Criteria

LADA is defined by three criteria set out by the Immunology of Diabetes Society. All three have to be present.

1. You were over 30 years old when your diabetes was diagnosed.
2. At least one islet autoantibody is positive in your blood — most often GAD antibodies.
3. You did not need insulin in the first six months after diagnosis.

Each criterion is doing a specific job. The first separates LADA from childhood Type 1. The second establishes that the cause is autoimmune, which is what rules out Type 2. The third separates LADA from Type 1 that happens to start in adulthood, where insulin is needed straight away.

The second criterion is the one that actually decides the diagnosis. Without a positive antibody, this is not LADA — it is Type 2 diabetes, however lean you are and however quickly your tablets are failing.

The third criterion has a known weakness worth understanding. Whether someone is started on insulin in the first six months depends heavily on the doctor treating them. Two people with identical biology could be split by it. So it is applied with judgement rather than as a strict cut-off.

You may also see the age threshold written as 30 or 35 depending on the source. It is a convention for research, not a boundary in your body.

The practical takeaway: a LADA diagnosis needs an antibody test. Nothing else can substitute for it.